As a Commons user, it seems unnecessary to confirm when I want to join a group

Adding "usability" tag.

I agree. Anything that helps for casual, public (social) users.

Agree. Make it easy. (remember how well everyone liked Windows Vista?)

I personally don't think it should be changed. There are 'Join' links all over certain pages, especially the group listing, making it very easy to mis-click. I'd rather confirm an action that accidentally join groups and have to go through the trouble of leaving them.

I think it would be okay if it worked a little like Flags... where, if you click Join, with ajax it turns into 'Remove' (you could even have less obtrusive confirmation process going the ajax way).

Of course, that seems a long way off though, because for example on a group homepage, all the ajax blocks and the activity stream would have to be refreshed to take account of the status change.