I've considered this question in some detail.
Actually I've seen many "spammers" who advertise their site and then get banned after one warning.
I've also seen unbearable trolls being given a long rope. Some of these trolls reach unbelievable heights of "trollsmanship" by the nonsense they spout regularly without contributing an iota to the community they belong to.
Yet these trolls are not banned because they don't break the "written rules".
What are your thoughts on this? How would you handle a regularly annoying troll as compared to an occasional member who "spams" or "advertises" their site on your forum?
Personally I prefer a "spammer" any day to a troll.