Eh, Google buying them makes a ton of sense.
1. Massive access to a social network that can better integrate all their products.
2. Integration with their ad platform (improving monetization enough to make it break-even).
3. They'd own one of the most influential social networks in the world. Google buzz, Google wave, Google + were all massive failures.
4. Integration with things like Google News. They'd be able to understand trends almost perfectly (from both news stories and users).
I think people on HN and the like sometimes massively underestimate why Twitter is so important. Twitter as a big social network like Facebook is never going to happen. Their decision to pursue that route seems foolish in retrospect. Instead, what Twitter has is a smaller group of users that are extremely influential. Moreover, they have the most effective fan-out messaging platform in existence.
I think focusing on monetization/user only makes sense while TWTR is an independent company. Companies like GOOG, MSFT, etc. benefit greatly from the externalities of owning TWTR more than the business itself (consider Youtube, for example).