Taking this a bit broader, the only way to track clickthorughs is to run clicks through a tracking domain, i.e. for www.alltheweb.com search for "help me out" without quotes, the results URLs are in the format
http://click.allthew...reeservers.com/. This means that when you click a URL, you go through am alltheweb server, that measures click throughs.
You can check by doing a search, right click on a link, select copy shortcut and see what the link says.
Google don't track clickthroughs, so click throughs can't be a part of their algorithm (if you are lucky, you
might get a Google tracked URL, as Google do spot checks of their SERPs).
AltaVista do use clickthroughs as part of their algo, and so
might, and I stress might, any other Search Engine that tracks click throughs.