In yet another sign that Web 2.0 isn’t just a passing fad fit for only wide-eyed startups with visions of grandeur, CIO Insight is reporting that Microsoft has a deal with Wachovia to provide the bank with a social-networking platform for its 100,000+ employees.

According to the report:

The nation’s fourth largest bank will roll out a social networking service for 110,000 employees over the next several months, giving workers a sophisticated knowledge-management platform that combines the user-friendly approach of the popular Facebook service with broad integration into Wachovia Corp.’s business applications.

The vendor for the big project isn’t one of the many contenders such as Visible Path, SelectMinds and Leverage Software in the burgeoning enterprise social-net market, or the ballyhooed Facebook itself. It’s Microsoft, which offers easy interconnection with other applications via its Office SharePoint Server product. Integration into the daily routine of business was a difference-maker in choosing the software.

So add Microsoft to the growing list of old-school, established tech companies jumping into the Web 2.0 pool. In fact, the pool’s getting a little crowded, with the likes of IBM and SAP already making their way to the deep end.