I was surprised to hear that 75% of Twitter traffic comes from the REST API. Surprised because I thought the number would be even higher. Twitter has slashed API limits in half across the board (even for its own official apps). Currently the public API rate stands at a miniscule 75/hour. The Fail Whale problem has been Twitter's own doing: they clearly should not have been making significant network changes as the World Cup started. They have not recovered and it's been an embarrassing month. Take a look at status.twitter.com (note: they aren't posting all the errors, the real picture is worse).