I know it seems a wholly unglamorous way to spend a Friday night, but I was just looking at the top all time most popular searches. Like most things I wonder about I haven't found a definitive answer...yet. I did stumble on aquarius, facebook, youtube, and hotels as being really popular so I'm going to leach a little power from them.
I have noticed that when I post song lyrics as subject lines, my blog appears in searches for that song or artist. Kinda cool. I would imagine that facebook and youtube are highly searched KWs because people like me will just type the name of where we want to go in our Google search box and then click through the search page because it's so much work to type a full URL.
Sorry, I just wasted 5 minutes of your life. This probably would have been more interesting if I had been hacked :)