If you're like me, you chafe at the limit on the number of groups you can be a member of at any one time.
SL vendors just about always have a group for those who like their work and want to be notified of new products or sales, and often the vendors sweeten the pot with giveaways to group members... but it doesn't take long at all to run up against the 25-group limit in SL.
There is a JIRA proposal to increase the limit, MISC-208. I hope you'll vote for it. The limitation on groups appears to be motivated by group membership being coupled in many cases with access permissions... but so many groups exist solely for notification and freebies that either the limits should be increased or some other mechanism created for the "fans of/shoppers at X" type of group.
If you find JIRA difficult to use, Cherlindrea of the excellent Fabulously Free in SL has an article on MISC-208 which includes instructions on how to vote for it. Please do check it out, even if this particular issue does not move you to action, because you should express your opinion on what problems are important to you and what you'd like to see improved in SL. (You might even want to vote for VWR-1258 or VWR-1080... Sorry, I couldn't pass up the opportunity.)
Thanks to Vint Falken for her post about MISC-208, which provoked me to mention the issue.