This is a free site and open community. However, all mods and admins have ability to ban. It happens for many reasons but there is one thing in common with all who have been banned to date...they earned it.
After seeing a flood of new folks this year, we need to make a few things clear again.
Things not to do:
too much promotion and no contribution
giving mods or admins headaches, thus wasting their valuable time, during or after they make polite requests. polite discussion is always fine. insults and bad behavior earn the ban hammer.
causing mods to have to repeatedly remove garbage posts, rants, or stupidity, because the user does not think before they pushed submit.
piracy support or posting pirated materials
and any other legit reason the admins or mods may come across