Aardvark is vark.com - as of February 2010 they are owned by the Google. It's part of a genre of question asking sites where the answer comes back partly from "your network" and partly from the random parts of the net that you don't know very much about. If you think you have an interesting question, you can ask it on Aardvark and see what you get. My practice efforts have been pretty dismal, but I might be asking for things outside of what it's capable of doing.
It might simply be that I've been at it too long and my non-random sources for answers to random questions are just better. If you've collected enough mailing lists full of local people or topical experts or reference librarians, the appeal of asking an unspecified audience is limited. Ditto the comparison with asking the same question to Twitter where it might ping-pong into someone's news stream, or asking a network full of PR people on HARO in the hopes of luring in someone's publicist who is happy to answer.