I've never had the chance to "run with a team", but I'm lucky enough that friendly people around my ability level will work with me during qually or a race if it's convenient. Sometimes we'll try to go out together to get a draft advantage.....sometimes it works, sometimes it doesn't. I know my current driving ability and confidence level being nose to tail through corners would not help me.
I have a fair number of friends who run with a team type setup, and there is a distinct advantage in the data sharing, sharing of spares if needed, and learning from different setups. During a test day once I signed up with Flatout for some data coaching, and was pretty amazed at how useful it was to have a top guy like Nick overlay his data on mine and Amy's and a few other drivers.
There are a few "informal" teams up here in the NE, LTD racing being the most famous (and probably the funniest). No hauler, no fancy tent, just a bunch of guys who hang out together in the paddock and take care of each other when needed. Every little bit helps, and being nice to your fellow competitors goes a long way towards cooperation and fair racing on the track.
-Vick