A Microsoft file hosting and synchronization service.
Seriously! Can't you fix a problem like that in a year? Actually, I only recently started having this problem, so I guess you're doing it on purpose. Why are you harassing your paying customers? Gross arrogance on your part!
Yes, they are doing it on purpose. New TOS item. Use Dropbox or Google Drive instead. Dropbox will prompt people to login, but there's a link to continue without logging in.