I was in the max number of groups prior to the update.... I cleaned it out a bit afterward and got down to 12 or so.
Then with the most recent update, Bungie made the group names and avatars bigger in the drop-down menu and I now had to scroll down in the list to get to many of the groups (including TWP, which is where I spend most of my time on bnet). This was unacceptable, so I left a few more. Now I'm down to nine. I still have to scroll down a bit to get to my favorite groups -- which is rather annoying -- but I'm having trouble finding any more that I'm willing to leave.
I was in 20, but thanks to the stupid new 10 group limit, when I received a 2 day ban from one group (which apparently temporarily kicks you out of the group now), I had to leave 10 groups in order to rejoin the one I was banned from.
[i]Thanks Bungie.[/i]