I was trying to think of Suze Orman's name while composing an email today. I could picture her face, and I know she's a popular speaker and author on personal finance. So I tried searching for different combinations of "female", "financial advice", "speaker", "author", "personal finance", etc. That didn't get me anywhere, so I tried searching on Google Images and threw "blond" in there. No luck.
Eventually, I gave up and went to Amazon to look for personal finance books. None of her books were in the Most Popular list, but a picture of one of her books happened to show up in the Listmania! section on the right.
I'm sure all of those social network companies maintain the kind of metadata on individuals that would be necessary for this type of search to work, but it needs to be web-accessible, and I'm not sure who would maintain such data on third-parties who aren't part of the network.
As an aside, Google also needs to update their advanced search so that date searches can be more granular than the current past 3/6/12 months options. Remarkably, Bloglines doesn't even support date ranges. Luckily, Straw, my aggregator, does. That allowed me to quickly find a post I had read this morning about yet another new social networking company.
The state is that great fiction by which everyone tries to live at the expense of everyone else. - Frederic Bastiat