Reminds me of when I had my account cancelled/suspended around 1982, the one and only time, with Republic Airlines out of Minneapolis. To beef up my account in the early days of FFP programs, I embarked on a number of flights where it was easy to jump off at the first stop but get mileage for the complete run, plus a couple of other system 'weaknesses'
I received a letter, (no email then) stating that I was abusing the program and my account was therefore terminated! An immediate apologetic phone call with what I remember, a very pleasant lady, resulted in me getting a slapped wrist, and agreeing to forfeit, I think it was around 25000 miles, which was fair enough under the circumstances.
I subsequently met her at a top tier members do, arranged by Northwest Airlines after their takeover, and we managed to have a bit of a laugh about it ! (But I never did it again! )