For a beginner? No, absolutely not. The last thing you want to be in is a team in your first year... There is too much to learn about speed, handling, racecraft, consistency etc, and all of these things are best learnt by driving. Lots. Only when you win regularly on pick up servers, even when starting near the back, and can pass/defend against anyone without making contact, even by accident, should you think about joining a team.
Then you have to choose a team - if this is the case, don't bother. Wait for a team to want you - you will be in a better team, with better drivers. Over 99% of LFS teams are rubbish, with no aims, rubbish drivers, and no results.
What can a team offer you? Support in leagues, mainly. Yes there is the social side of things, but that can be had via forums, MSN and real life visits. You don't need three letters in front of a name to be a friend.
The big question is - what can YOU offer a team? Can you arrange and run a league? Run a website (properly, not a crappy free one)? Can you make software that will aid the team? Are you gifted at sorting race strategies or managing a driver(s) in a competative league??
Chances are you won't get quicker in a team, you won't make any new real friends, you won't get glory, money, or generally better. It just means you have to do leagues (otherwise what is the point of a team?), and wear the team skins, and dedicate time to helping the team in whatever way you arrange.
If it's just a 'friendly team', solely for people to chat, and race with known people then isn't that a bit pointless? How is the racing or the chat improved with three letters in front of your racername?
I was in three teams. The first was formed by Will Dendy, and it was him, Kirves and myself. Will spent ages pursauding me to join, and I was already a quick driver by then. That was then taken over by vMax, run by James Burgess. I was happy there for several years, and did various leagues for the team, and assisted in running the team later in my time. We were never a top team in LFS, mainly because we had no direction - I believe they were better in NASCAR. But then Triple7Racing came a knocking, and it was too good an opportunity to miss. It started well, and I tried entering leagues, but real life was taking up too much time. I tried to stay, hoping that I would get the chance to race in T7R colours again, but I eventually realised I was just taking up space that a better, more committed driver could use, and so I left (hopefully on good terms - I certainly have nothing bad to say about any member of T7R past or present). I don't think I'll join another team, even if real life allows me several hours a week in LFS again (rather than an hour per month, max), because they can't offer anything I want that I can't get without a team, and I can't offer a team anything they need.
In short - don't bother with teams unless you plan to race in lots of leagues with the same people.