I'm afraid it's not a very interesting explanation...
We have a simple set of forum rules that each member agrees to when they join our Camaro enthusiast family. If someone breaks those rules, they get a warning. If they do it again, they get a 10-day suspension to think about it. If they do it again, 30-day suspension...any more, and it becomes permanent.
In an effort to prevent the forum from becoming fractured and "skipping" between posts...a suspended members posts are not removed...so you see "suspended" under their name, instead.
We're not unreasonable, and it's not fun...believe me, I don't wake up in the morning eager to remove anybody from the forum...I have real teenagers to deal with.