Many/most of us have never experienced a forum ban, and those that have rarely earn more than one. The process is that subscribers can click the "alert moderator" button if something annoys them, and enter their reason in the report which the mods see. Mostly the mods don't ban on their own account, they work off the Alerts Report and have to check the original posts/threads before they do anything. So if a ban of any kind has been issued, it has to have been bad enough to annoy at least two paying site members. Spamming - one definitiion is "posting frequently and irrelevantly in practically every thread, even if you have nothing to contribute to the discussion and are simply disrupting the dialogue with an empty link-only post" - is a bit like a small mole in an awkward spot. Mostly it doesn't bother you, but after you've bumped it 27 times in 10 minutes you're about ready to take a knife to it!
The unpaid moderators on this site do a good job in my opinion, it's a thankless task, damned if you do and damned if you don't.