Missed opportunities are a painful thing to reflect upon.

Take the case of Ericsson (NASDAQ:ERICY), one of the best telecom-equipment companies out there. We all could have had our shares in this Swedish tech giant for a single-digit price just three years ago. Sure, that was the nadir of the tech-wreck aftermath, but it just goes to show once again that the markets are anything but efficient, and that they periodically give us all the chance to scoop up great companies at ridiculously low prices.

Judging by the fourth quarter, we're not likely to get a second crack at those ridiculously low prices anytime soon. Sales were up 16%, and while the gross margin eased off slightly, the operating margin held steady and the company saw reported net income jump more than 50%. Not only did Ericsson do well in its core equipment and services business, but the joint venture with Sony (NYSE:SNE) is also performing nicely, with shipments up 28% and sales up 15% in this recent quarter.

It's looking like 2006 could be a good year for mobile infrastructure investment, and Ericsson should be exceptionally well-placed to benefit. Not only does the company have a growing service/outsourcing business, but supposedly 40% of all mobile calls go through Ericsson equipment. I couldn't independently verify that number, but if it's true, it's quite a testament to Ericsson's success, and a fair reason to believe it'll continue to stand up well to the likes of Nokia (NYSE:NOK) and Nortel (NYSE:NT).

Speaking of infrastructure investment, I would expect to see the likes of Deutsche Telecom (NYSE:DT) continue to spend on T-Mobile. Likewise for Cingular (owned by AT&T (NYSE:T) and BellSouth (NYSE:BLS)). And that doesn't include all the carriers in Asia looking to upgrade and build out their systems.

There's still a fair bit of analyst disagreement about Ericsson (some say "buy," others say "sell"), and that often speaks both to opportunity and risk (opportunity in the sense that there are still those left to be convinced, and risk in the sense that maybe the "sell" folks are on to something). While I wouldn't side with the "sell" folks wholeheartedly, I don't see the shares as overwhelmingly cheap.

For more mobile Foolishness:

Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).