Droid,
You can see the reason a member was banned here:
http://www.therpf.com/f15/member-updates-91522/#post1339016
In regard to Darth Darren, he was a sockpuppet of a previously banned member.
To answer your question, the general overriding principle for why most people get banned comes down to a simple equation of liability outweighing contributions. If you are more of a pain than an asset, you won't last long here. If you are a positively contributing member and add to the community, you have little to fear. If you are constantly pushing boundaries, trying to find loopholes in the rules, stirring up trouble and inciting the staff and/or the membership, you won't make it very far. If you are here to scam members or take advantage of the sites resources, you won't last long. Aside from that, as GNDN said, just read over the rules, and if you have any questions, we will be glad to clarify them.