I was thinking along the same lines. Leaving ill-fated attempts at social like Wave and Buzz aside, most of Google's products have been about getting things done. Especially search. You look for something, it finds it. That's all. It's essential that the "application" gets out of the way here and finds what you were looking for as quickly and accurately as possible. To make that happen, technology is needed that is very complex, deep, with almost everything happening behind the scenes.

Social networking sites/apps are, by definition, completely different beasts. They're shallow (I don't necessarily mean this in a negative sense BTW), they don't get out of your way, and users generally don't want them to. That's why sites like Facebook don't just have a list of friends, but are crammed full of games (many of which are "social" as well), videos, pictures, ads, polls, questions, suggestions, etc.

Building a system like this is diametrically opposed to what Google has been doing. So it would make sense that they aren't good at it... it's just not what they do. But I can understand that they might feel they need to produce something like this, otherwise they're going to miss out on the Next Big Thing. If people are spending all of their time on Facebook or wherever, and Facebook decides to add a decent search engine, well... =/