If you needed any indications that the stock market has been unstoppable over the past five years, here's another: just shy of half of the approximately 4,700 stocks in The Motley Fool CAPS Screener database are trading at or within 10% of a new 52-week high. For skeptics like me, that's an opportunity to see whether companies have earned their current valuations.

Source: Ryan McFarland, Flickr

Keep in mind that some companies deserve their valuations. Take Enterprise Products Partners (NYSE:EPD), the nation's largest midstream provider, as a great example. While commodity pricing and weather concerns will always lend to some degree of skepticism about pipeline stocks, Enterprises' greatest advantage is the fact that investing in our pipeline infrastructure is a necessity. New shale finds both on land and offshore, coupled with growing global energy demands, are only going to put middlemen like Enterprise which transport and store energy assets in the forefront. This is not the type of company short-sellers want to stand in the way of.

Still, other companies might deserve a kick in the pants. Here's a look at three that could be worth selling.

What's on your plate?
Consolidation in the cable service space has everyone on the edge of their seat lately. Comcast buying Time Warner Cable and AT&T gobbling up DIRECTV will create two cable behemoths that consumers worry will reduce competition. More than that, it leaves poor DISH Network (NASDAQ:DISH) on the outside looking in. These two megamergers have pushed DISH to pump out innovative new ideas that'll help jump-start its growth.

Recently, the satellite service provider announced it'll be the first to offer a legal Internet pay TV service. If you recall, Aereo was deemed by the Supreme Court to be operating illegally given that it didn't share licensing fees with broadcasting networks. DISH is doing things the right way and could benefit from its first-in-class move.

In addition, DISH also introduced a wireless set-top box. The hope here would be that consumers would appreciate the lack of wires, which it's been heavily touting in its advertising campaigns, and switch based on that convenience.

Source: DISH Network

Yet, for all of these positives, one concern remains: a lack of genuine subscriber growth. Even with its churn rate dropping 5 basis points to 1.42% in the first quarter, DISH was only able to add 40,000 net subscribers to 14.097 million. The only way DISH has been able to maintain profits lately has been through price increases, with the average revenue per user jumping to $82.36 this past quarter from $78.44. Modeled as the low-cost leader next to DIRECTV, if DiSH is forced to continue raising prices it'll lose the primary pricing edge it holds over its primary competitor.

If stagnant subscriber statistics weren't a big enough concern, DISH's valuation is an even larger problem. Despite new product introductions, DISH's long-term growth rate is probably around 5%, give or take a percent or two depending on the U.S. economy. Yet, DISH is currently valued at 33 times next year's earnings, pumped up by some wild speculation that it still might be a takeover target. With little in the way of growth and no dividend there's just little blood left for investors to squeeze out of this turnip. I'd suggest investors look elsewhere for a compelling valuation in the cable service sector.

Not "fixed" yet
If you look up "inconsistent" in the dictionary, you just might find a description of Orthofix International (NASDAQ:OFIX) there, a supplier and developer of medical devices and orthopedic products used most commonly in spinal fusion processes or for bone regenerative purposes.

In 2012, Orthofix sold off its sports-medicine unit for $157.5 million so it could instead focus solely on its spinal and bone regenerative product line.

Source: Orthofix International

Since then it's been orchestrating a seemingly endless turnaround that's moved forward literally an inch at a time. With the introduction of the Affordable Care Act in the U.S., medical device makers have struggled with the 2.3% medical device excise tax, as well as insurers and patients who've been less likely to undergo surgeries deemed elective. The end result has been generally flat sales growth for Orthofix and a series of on again, off again full-year losses.

Of late, though, Orthofix shares have soared, primarily because of the address on the front door of its headquarters. Based out of the Netherlands, Orthofix could offer a larger medical device company in the U.S. an easy way to escape corporate taxes that can hit 40% on the high end. With a top marginal corporate tax rate of just 25% in the Netherlands, a larger device company could save millions by purchasing Orthofix. In response, shares have rallied about 80% in just five months.

As you might imagine, I don't believe this move is justified given the current growth potential for spinal products. While this might appear to be an area of high growth on paper, an ACA-induced procedure drop coupled with a growth rate in the low-to-mid single-digits simply doesn't correlate with its forward P/E of 25. Essentially, investors here are simply banking on a buyout for a company that's not expected to grow at a quick pace and has proven to be historically inconsistent. Exactly how much of a premium should these investors really expect?

My belief is that Orthofix shares are already fully valued and that investors wanting to take advantage of the medical device market have plenty of other paths they can take with stronger growth prospects and a considerably more reasonable valuation.

Printing a fairy tale ending
Sometimes with this series I have to suggest companies whose products I like and use that could head lower -- this is one of those instances. The last company up this week that you may want to part ways with is printing services and enterprise software specialist Lexmark International (NYSE:LXK).

Source: Sir Adavis, Flickr

Lexmark is currently undertaking a mammoth restructuring campaign meant to put its inkjet printer and hardware business in the rearview mirror in favor of its managed print service and software portfolio. In the first quarter Lexmark noted that its managed print and software segments combined for 18% year-over-year growth and now account for 28% of total revenue, up from 23% in the year-ago period.

The company also recently announced a 20% dividend hike in an effort to reward shareholders who've stuck with Lexmark during its turnaround campaign, and also to demonstrate that its cash flow is strong enough to pass along additional perks to shareholders. The current yield of 3.2% is certainly substantial given how pitifully low yields are for CDs and most bonds.

But Lexmark's push into enterprise software isn't just a "Wham. Bam. Done!" type of shift. This is a multiyear product line shift that involves forging new customer relationships in an area where it wasn't a powerhouse previously. In other words there are likely to be hiccups along the way regardless of what its current growth rate might signify.

Also consider that its hardware and legacy printer business are going to continue to drag down whatever positives might be produced from the printing service and software segments. Hardware revenue fell 8% last quarter while total supplies dipped by 1% year-over-year. This legacy business is added weight that's likely to act as a drag for years to come.

Investors would certainly appear to believe that Lexmark has turned the corner given that shares are up around 150% since mid-July 2012, but a closer look at its top-line reveals that sales decline are expected throughout the next couple of years. The real reason Lexmark has rebounded is tight cost cutting. But cost-cutting is only a temporary solution to a long-term problem.

Until I see growth from Lexmark's top line and a concrete evidence of its ability to forge lasting enterprise partnerships I'd suggest watching this stock from afar.