Welcome to WebmasterWorld Guest from 126.96.36.199
Forum Moderators: rogerd
1) Cookies. It is an APS.net forum and wanted to share login information (including persistence) between the forums and the main website.
2) SEO. I feel that SEs are considering more site wide factors as opposed to just page factors. So I believe having 1000s of user generated content on my topic strengthens my main site.