Yeah that was a huge controversy yesterday. Unfortuantly no one could really explain what was actually changed in 140 characters or less (oh the irony), but techcrunch has a little write up on it here:
http://www.techcrunch.com/2009/05/13...when-you-cant/
and you can read about the 24 hours of twitter hell here.
http://www.techcrunch.com/2009/05/14/twitters-spectacularly-awful-24-hours/