Studying Google Analytics this morning for my used cars classified site, it appears in the last month, no less then 1376 different combinations of searches brought people to the site. The most bizarre ones are searches for completely different domains, like "www.unusedcar.com". I'm not sure which search engine would return my site as a valid result for that. Also completely unanticipated are the number of slang words people use to search, like "looking for dirt cheap cars", and perhaps as a factor of the large amount of hits I get from ask.com, "what web page can i find cars for sale only by owner". When I first started the site back in 1995, before anything about SEO was known, the only thing I thought to search for was "used cars". That is still the most popular way to get to us, but it only makes up 17% of the total.
I was able to get in on the first round of Google Analytics last November, but I would have killed for something like this ten years ago, when everything with search engines was superstition, and a change in meta tags could result in a huge drop or gain on search (before Google came around).