I don't get it. Investors should have seen this one coming. But judging by the fact that shares of transaction management software firm Synchronoss (NASDAQ:SNCR) rose 10% in early trading Tuesday on news that the company teamed with Sprint Nextel (NYSE:S), something is amiss (the stock is down around 9% since the close on Tuesday). Never mind that CEO Stephen Waldis openly said that it was close to signing another tier-one mobile carrier when it reported third-quarter earnings a little more than a month ago.

With the Apple (NASDAQ:AAPL) iPhone now fueling it, AT&T (NYSE:T) generated 78% of the firm's revenue in the recent quarter, so investors were rightfully happy to hear about efforts to diversify. To this end, Synchronoss also emphasized that it is seeing a larger contribution from other customers such as Clearwire, Cablevision, and Vonage (NYSE:VG).

The company is also moving quickly into international markets, particularly Europe, where it is teaming with local system integration firms already familiar with carrier and back-office systems. With its success in the U.S. with its activation product for the iPhone, it's likely that Synchronoss is working with Deutsche Telekom's T-Mobile, France Telecom's (NYSE:FTE) Orange, and Telefonica's (NYSE:TEF) O2 on their respective rollouts in Germany, France, and the U.K.

Still, announcing that it's adding a struggling U.S. carrier to the roster doesn't seem like it should significantly affect the stock price. It's likely that the wild swings in Synchronoss' price are fueled by speculators trading in and out of shares of the recent IPO. It's hard to blame them -- any company that's riding the iPhone's coattails these days is bound to be a fervent topic.

With the rapid growth and high-profile customer list, it's also likely that stock in the company will never be cheap, so investors looking to tap the Synchronoss opportunity should tread carefully. Chances are, you'll pay a steep premium for a volatile stock that knows few bounds.

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Fool contributor Dave Mock owns no shares of companies mentioned here. Dave is the author of The Qualcomm Equation. Sprint Nextel is an Inside Value recommendation. The Fool's disclosure policy drives on the right side of the road.