I think this issue has far more potential to be a Twitter-killer than downtime problems. One of Twitter’s distinctive features is its SMS capabilities. If those start going away, then what is the draw of the service?
European users of Twitter can no longer receive text message updates on their cell phones, in a temporary move designed to keep the start-up's telecom bills down.
Twitterers can still use its U.K. number, +44 762 480 1423, to send updates to the site. But that number will no longer deliver text-message updates back to users, and recommends that they use the Twitter mobile site or a third-party client like TwitterBerry, Twitterrific, TwitterMail, or Cellity.