Groups was an awesome service when it launched back in 2001. It was the search engine to go to if you wanted to search UseNet, which (in the pre-Friendster/MySpace/Facebook days) was the largest social network on the Internet. Google slapped a much nicer UI on it than DejaNews ever had, rivaling desktop Usenet readers but without the need to download anything or run another program.
It started sucking when they took UseNet out of it - then it became just another mailing-list site in an already crowded field. (Granted, UseNet itself was nearly dead at this point.) And the field was shrinking, since more affinity groups started moving to FaceBook, or MeetUp, or getting their own individual sites on the Internet with stock forum software. And IMHO, it really died when it went to the AJAX UI - there's no real reason for a content site like Groups (or Blogger, for that matter) to go heavily AJAX, it just makes it feel clunky.
Seconded. The AJAX UI sucks the most of all. Try loading up 100 pages of threads on one screen, selecting 19,850 spam threads to delete, and finding out an hour and a half later that your request is too large and all your work is lost.
It started sucking when they took UseNet out of it - then it became just another mailing-list site in an already crowded field. (Granted, UseNet itself was nearly dead at this point.) And the field was shrinking, since more affinity groups started moving to FaceBook, or MeetUp, or getting their own individual sites on the Internet with stock forum software. And IMHO, it really died when it went to the AJAX UI - there's no real reason for a content site like Groups (or Blogger, for that matter) to go heavily AJAX, it just makes it feel clunky.