here's the current setup. skimlinks wraps google analytics to give semantic-web style analytics on visitors to the forum (not members, just guests). it gives the usual google analytics: referrers, time spent on the site, exit paths, etc. i believe skimlinks also tries to pull some more structured information out of this. it tries to determine what interests guests, whether they consider signing up, what the conversion rate for signing up is, and what metrics correlate with signups.
here's the technical information on what and how it tracks:
http://skimlinks.com/visitor-cookiesyou can turn it off as a guest by simply disabling cookies for our site, or by opting out of google analytics, since the core metric are gathered by google. the thing about guests is that, obviously, they don't post. however, guests visitors are in the majority of users present on any forum at any given time. we have a pretty good idea what helps you guys since you post and can be vocal about what improves the community, but the guest contingent is, by definition, silent. skimlinks obviously pushes their monetization services, but that is how _they_ monetize their userbase. However, they offer their wrapper and analytics engine for free as well as kind of a carrot-stick thing.