I have several niche sites and they all utilize analytics. Recently I noticed that one site in particular has the number one spot in google for the keyword I'm targeting and for some strange reason, google unique hits come in second place as far as traffic after webcrawler. I was wondering how this site was picked up on the webcrawler search engine but all of my other sites are not. It seems to have a huge potential for traffic.
Webcrawler is itself a search engine that uses an amalgamation of results from all other search engines. You also have an option to see results based on individual search engines. I am not exactly sure of it popularity and the mechanism used to blend the results from all the major search engines, but if your are getting more traffic from webcrawlers why not go ahead and check how you rank for your keywords on this search engine. They also have paid inclusion services (like any other search engine), the only difference, they intersperse organic and paid results on the same page.