Overload?

I would be interested to know what happened in the last few hours.  A lot of internet sites were inaccessible until about an hour ago -- including Twitter.  The problem had the earmarks of an overload condition but why?  A DDOS attaclk?  Surely those are routinely  defeated these days?  Though it was notable how suddenly everything became accessible again.  My best guess would be that all the uproar about judicially mandated homosexual marriage in America overloaded a lot of sites that feature comments.  Maybe the news will tell us all in the next few hours what it was all about.