Well, you can't ask why a specific member got banned because that will possibly get you a short vacation. Most members who have been banned were repeatedly warned to knock off certain behaviors/comments. They continued, so they got banned. Others have been banned for creating a second screen name and using it while still using the first. Sometimes a second screen name is allowed, such as the case of a vendor posting under the vendor name, or posting under their own personal name.
It is possible to get a short vacation, but not get completely banned. Continuing a certain behavior after a vacation usually results in a complete banning of said party.