Twitter's New Rules Restrict Usage Via Rate Limits
Although the social networking giant has a vast network of computers, if you consider the effect of millions of users pinging their servers frequently while looking for updates, they can't be blamed for the new rules. If the limit is met, you'll see a "Sorry! You've hit your hourly usage limit! Try again soon" message.
If a user, app or bot hits the limit, nothing will happen--that is, nothing at all will happen on the throughout the site. Twitter puts the user or app into a time-out which lasts 10 minutes. Then the access restriction is lifted until the next over-limit occurance.