Going through old threads, I see alot of user names, and then under the name, or next to it, it says EX-Member.  Did those people get banned? or is their some way to become an X-member?

Those aren't the members that have been banned. They are the ones that removed their own profile for one reason or another.

The weirdest thing, that happens alot on the flea market board is see "ex-member" next to someone who just posted something for sale.  I don't understand?  :-?

Most of those ex-members are a one time post.  They are usually deleted, but sometimes they are overlooked.