Microsoft's purchase of semantic Web search company Powerset on Tuesday highlights a common theme running through the company's technology portfolio: A growing number of Microsoft's products are stamped with the words "Not Invented Here."

From search to security to advertising software, Microsoft is increasingly bypassing the work of its own R&D labs and turning to acquisitions to buy its way into the tech industry's hottest growth markets.

Powerset, which Microsoft reportedly bought for more than $100 million (Microsoft has not officially commented on the deal's value), marks the company's ninth acquisition in a year that's only half over. By contrast, it took Microsoft a full three years to make the same number of deals between 2001 and 2003.

Beyond Powerset, other key deals for Microsoft this year include a $1.3 billion agreement to acquire enterprise search specialist Fast Search & Transfer, a $100 million buyout of desktop virtualization vendor Kidaro, and a $100 million purchase of computer reservations system Farecast.

And there's the big one that got away -- the failed plan to buy Yahoo for $44.6 billion.

Analysts say two factors are behind Microsoft's acquisition binge: The recent emergence of a mergers-and-acquisition team, led by CFO Chris Liddell, that is philosophically more disposed to mergers and comes armed with a $26 billion cash pile, and a business innovation cycle that even the biggest corporate R&D labs can't outpace.

For instance, Powerset specializes in an esoteric form of Web querying called semantic search. The technique uses a variety of linguistic tools to interpret the meaning of search phrases to produce the most accurate results. The method has been in development for more than 10 years.

"You can only make so many guesses in an internal lab about where the world is going to go," said Rob Enderle, principal analyst at the Enderle Group, in an interview. "But the world makes millions of guesses in the form of smaller companies that come up. The probability that something significant is going to be developed outside your company as opposed to inside is much higher."

Enderle says other big vendors, including IBM and Hewlett-Packard, are faced with the same odds and are ramping up their acquisition efforts.

The danger, for Microsoft and others, is ending up with product offerings comprised of a series of clunky bolt-ons rather than truly integrated technology suites. "The key is finding the right balance," said Enderle.