The Eyes Service is used to keep track of the HTTP referer header. This allows a user to display links to pages that link to their page. Its a "who's linking to me" service.
What's that you say? So if Google could index the links in the Eye's module it would allow lesser known sites to become more popular just by adding links to popular Aim Pages on their site. Doing so would result in their URL showing up on those sites (assuming they were using Eyes) and would therefore increase their ranking.
This also serves to increase the popular pages ranking too as more people will link to it to try to increase their ratings. :-)