When one major tech company plunks down billions for another--think Microsoft buying Nokia--everybody pays attention. The vast majority of deals, however, don't make headlines. They involve low-profile startups and purchase prices in the mere tens of millions of dollars. But that doesn't mean they're insignificant. In fact, they can tell you an awful lot about where the industry's best-known names are headed.
In most cases, the acquirers don't care about the products they've bought. (To prove it, they often instantly shut them down, as Yahoo did with Rockmelt's smartphone browser in August.) What they covet is the expertise of the acquisition's...