Firstly, we will never automatically charge you if you go over your limit. We'll first reach out to you by email to let you know that you're over the limit with the option to pay for additional capacity to tie you over for that month. Prices are just $10 per 1,000 MTU's.
If we don't hear anything back within 14 days, we will let you know that your HelpShelf widget has been downgraded so that stats and logs are no longer being tracked and help content can no longer be searched for. Once the 1st of the next month is reached, and your quota has been reset, your HelpShelf widget will be automatically put back into normal operation.
It's also worth noting, that downgrading your widget will in no way prevent your customers from reaching you. In effect, you will just lose your management reporting and the ability to have popular/frequent content tracked, calculated and served to your users.