In this weekly column, I like to pick on companies that are coming undone, plagued by crumbling fundamentals and unsustainable share prices. However, sometimes I have to throw out a stock that appears to be doing everything right. This week's candidate is trouncing Wall Street expectations while it heads into a promising turnaround.

Naturally, it wouldn't be right to dismiss a company on the rise without offering you something better. I may pick on a stock, but I'll come right back and restock with three companies that I think will be better replacements for your portfolio.

Who gets tossed out this week? Come on down, SanDisk (NASDAQ:SNDK).

It's a flash flood
When it comes to flash-memory products, SanDisk is the first name that should pop into anyone's noggin. From digital cameras to cell phones to USB thumbdrives, flash storage is as popular as ever.

SanDisk stumbled during the early stages of the recession, posting four consecutive quarterly losses through the first quarter of 2009. The company has bounced back quickly, though, blowing past Wall Street's targets with better-than-expected earnings ever since.

I'm a fan of upward revisions, and SanDisk is certainly praiseworthy. Over the past three months alone, analysts have gone from projecting a net income per share of $0.35 in 2009 and $0.46 in 2010 to $1.33 and $1.53, respectively.

The stock has responded to the turnaround. Shares of SanDisk have popped nearly sixfold since bottoming out 14 months ago. Are the gains warranted, especially as momentum points to yet another analyst-thumping quarterly report next week?

I think not.

Problems in the long run
IronKey, the niche maker of what it claims is "the world's most secure flash drive," has never shied away from hammering away at the vulnerabilities of larger rivals SanDisk, Kingston, and Verbatim. It may finally have a worthy mouthpiece, now that it's teaming up with Lockheed Martin (NYSE:LMT) this week to introduce Lockheed's IronClad line of USB drives.

When a defense contractor enters your industry, you know it means war. Sure, the IronClad will never be more than a high-end specialty product. However, its very presence will help expose the security shortcomings of easily hacked encrypted drives. This isn't a competitor -- it's an eye-opening educator for consumers.

That immediate threat leads us to longer-term relevancy concerns. Earlier this month, Google (NASDAQ:GOOG) introduced a free gigabyte of cloud-computing storage to Google Docs users. That may not seem like much, but let's think bigger-picture.

Right off the bat, Google's move is a shot at casual SanDisk USB drive users. If someone needs to move files around, uploading them to a secure cloud to retrieve on a second machine makes sense. The two drawbacks to cloud storage -- speed and connectivity requirements at both ends -- are certainly limiting for now. However, aren't we evolving toward perpetual connectivity at ever-faster speeds? In time, how important will flash drives be? If our future will always be within earshot of a distant server's storage, what will become of SanDisk's drives, cards, and readers?

SanDisk has struggled when it tries to think out of the protective commodity box. Its Sansa portable music players are no threat to Apple's (NASDAQ:AAPL) iPods. Its slotMusic cards are the duds I knew they would be. It's rolling right now, given the growing number of devices that rely on flash memory. But since when is technology forever? Even for solid-state drives, but the state of technology is anything but solid.

Good news
As I do every week, I don't talk down a stock unless I have three alternatives that I believe will outperform the company getting tossed. Let's go over three new fill-ins.

Sierra Wireless (NASDAQ:SWIR)
If portable connectivity is the foe of flash, the Overdrive mobile hotspot that Sierra introduced at this month's Consumer Electronics Show should strike a decisive blow against SanDisk. It's similar to the MiFi that Novatel Wireless (NASDAQ:NVTL) rolled out last year, but it could be substantially faster, since it's a 4G device. Anywhere the Overdrive goes, hotspot connectivity is a button-press away. Analysts see Sierra Wireless' earnings growing by 51%, to $0.77 a share this year. The stock is more than reasonably priced here in the mid-teens.

Amazon.com (NASDAQ:AMZN)
On the surface, Amazon is more friend than foe. It sells plenty of SanDisk products as the leading online retailer. Its initiatives to replace physical books, CDs, DVDs, and video games with digitally delivered alternatives also bode well for flash storage in many cases. However, Amazon's S3 is also a giant in cloud storage. Sure, its growing server farm is dedicated mostly to developers, but that only means that it's getting its pedigree papers in order for when cloud computing goes mainstream as a flash replacement.

Google
One can argue that cloud computing is already popular with the masses, since free online email -- including Google's Gmail -- is already the cloud incarnate. Google isn't the largest email provider. It isn't even the first to offer up free data storage (since Hotmail beat it to that punch via SkyDrive). However, Google wasn't the first search engine, either, and look how well that played out. If consumers want free, ad-supported storage, Google will be the top dog in providing and monetizing it. Yes, Big G's stock has been a speedster during the past 10 months of rallying equities, but it's now trading for just 22 times forward earnings projections. That's not cheap, but Google isn't supposed to be cheap.

Sorry, SanDisk. I'll think of you kindly, even as your memory fades.

Google is a Motley Fool Rule Breakers recommendation. Apple and Amazon.com are Motley Fool Stock Advisor selections. Try any of our Foolish newsletter services, free for 30 days.

Longtime Fool contributor Rick Munarriz always takes out the garbage. He does not own shares in any of the stocks in this column, except for Novatel Wireless. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.