I've seen other forum administrators say the same thing in the last few days: they're getting hammered with spam sign-ups. Apparently a major spammer was taken down, and they're seeking other outlets.
I know that one domain I own and administrate, which is nothing but a low-volume private forum, just got a 509/bandwidth shutdown, when I've never been anywhere near the limits. Suddenly it jumped to more than double the 3000 MB limit.
I don't know what's going on, because for more than 48 hours now I haven't been able to get any response from the hosting company, and they won't even let me log into the cpanel to see where the bandwidth was used. They didn't block ftp, so I was able to copy all the contents in case I have to jump ship early. I'll definitely be doing that when the contract is up in February.
FYI, hostingbegin.com is cheap, but has zero customer service.