This actually sounds like an interesting idea to me. Most of the time, I suspect, my search results don't need data from my social network to improve. But occasionally social data might be highly relevant. And so if my search results are Google quality most of the time, and even better (due to social network hits) a small percentage of the time, Cuil may totally rock.

I also like how this isn't a social network search engine. It's an extension of normal search. I can't imagine myself (at least today) sending a separate query to my social networks. But obviously I query a normal search engine all the time.

I wonder if they will run into Terms of Use issues with Facebook et al. In order to search efficiently, they'll need to store social network data...