netmeg - 5:07 pm on Feb 9, 2011 (gmt 0)
Watching internal site search reports for queries that get zero results - this has been excellent for some sites. The idea is this. If visitors are looking for a topic, then we ought to have something for them. It's a real demand from real people. When we create supply for that demand, the amount of SE traffic can also be amazing.
Funny you should mention, I just started paying a lot more attention to this in recent months. I'm also crafting custom "item not found" pages for some of these searches - if it's a product we're out of temporarily, I'll get their contact info to let them know when it comes in, and if it's something we don't carry at all, I'll use a page that suggests some alternatives. Not sure that counts as SEO though.