Yesterday, when I pressed the “Stumble” button of the StumbleUpon toolbar, I was greeted with this rather rude error message saying that my StumbleUpon account has been temporarily disabled due to “excessive use”.
Luckily, this was not an official warning from StumbleUpon but a prank page created by some anonymous user. Lot of other people seem to think that this is real and the site is therefore a big hit already at least among the SU community.
Related: Use StumbleUpon without installing toolbar