Blizzard accidentally leaked something called the "Starter Edition" of Diablo III on Battle.net accounts - whether the user was part of the Diablo III beta or not. This forced Blizzard to shut down the beta servers for the time being.
According to community manager "Nethaera," an update on the outages will be posted around 11:00AM PST (7:00PM GMT). For now, the servers are "unavailable until further notice."
Gamers who checked out the "Starter Edition" found that it was the same build as the beta version of Diablo III, except it would occasionally ask the user if they wanted to get the "complete game".
This seems to indicate that there will be a trial version of Diablo III released, sort of a limited feature shareware copy or a full featured demo that will be given away free to entice gamers into getting the full game.
Diablo III is due to be released on the 15th May on PC. The beta is due to on the 1st May.