At the Investor Relations Blog, Dominic Jones makes an excellent point:

THE spotty success rate of mergers and acquisitions in creating shareholder value has long dogged investors who must try to decide whether a proposed acquisition by a company they own makes sense.

But with the advent of employee bloggers on the open Internet, especially those who work for leading technology companies, investors may be getting valuable insights into at least one factor that can make or break a successful deal: corporate culture.

In the ongoing Microsoft/Yahoo saga, there's been plenty of discussion of the severe mismatch between the two corporate cultures. (Way too much for me to provide links!) Jones quotes a Yahoo employee: "I estimate that 1 in 10 Yahoos will refuse to work for Microsoft". (I'll add: mere numbers don't tell the story; it's the best technical staff who are most likely to leave.)

Here's more from the Yahoo employee's blog:

Key reason #1 - Microsoft is anti open-source, Yahoo! utilizes open source technologies extensively.
...
Key reason #2 - Microsoft is evil, Yahoo! is not.
...
Key reason #3. Microsoft technologies suck.

(Note that it doesn't matter whether any of the above are objectively true, only whether Yahoo folks agree.)

How about some views from inside Microsoft? Mini-Microsoft is worth a read:

Feb 1:

I'm surprised yet not surprised. Internally, a number of us had heard reasons from Steve Ballmer why a Yahoo! acquisition didn't make sense. One that sticks in my mind right now is how if we acquired Yahoo! - such a big company - we'd have to naturally have layoffs within Microsoft to accommodate it.

Feb 10:

Microsoft's Yahoo! Acquisition is Bold. And Dumb.

Please, Yahoo!: fight to stay independent.

There's plenty more where that came from.