We all know why they're doing it but I am not happy about it, not because of your problem, OP, but because I block non-payers and troublemakers via email address so that they can't make a duplicate account and buy again. When I used to simply block their username, they'd often turn up a few weeks later with a new account, but blocking emails has seemed more effective.

And before anyone tells me to require immediate payment - 80% of my orders are multiple items, so that doesn't work for me.