I would, a few times per year, spend $10 or $20 to promote some tweets on Twitter. At one point, I stopped being able to do that, due to some nebulous "violation" of their TOS. I've gone back and forth with them a handful of times, and they always basically say "Yep, we looked into this, and you definitely did something bad, but we won't tell you what it was or which tweet it was in." They still send me emails and other ads trying to get me to buy advertising, though. I don't really care, it is just kind of funny.
I don't know why they all are so bad at customer support.