Same situation exactly. I tried emailing them to dispute it, or at least try to figure out what supposed "commercial use" they suspected, but nobody ever replied. Plus, I think I may have only ever used it for like 20 minutes a month to do stuff like move a recipe into Dropbox so I could share it with a coworker, or start a Steam game downloading. I guess those 20 minutes a month must have been judged to be critical business use, sufficient to earn a threatening email.

I don't miss them or their service.