LinkedIn is one of those sites that you hate but use. It is boring. It has horrible user interface. But it is useful as a secondary professional network — to loosely stay in touch with professional acquaintances.
There is however one ridiculous problem with how it support groups. You can setup a group for managing communications between people within that group. It should be useful for non-profits, SIG’s, etc. I recently setup a group for the people who attended the iPhone bootcamp in Boston. Often you want a group’s membership to be approved by the organizer. Here is the catch — LinkedIn will not notify the organizer if a group membership request comes into LinkedIn. So you have to log in and check for requests. That screen is of course four clicks away. Tedious.
This bug is actually documented on their website here.