Bashiok announced on the World of Warcraft forums that there will be a system put in place for Diablo 3 players to reset their skill points, allowing more ease of experimentation with skill points as you gain, or even just allowing you room to mess up once in a while, and not have to make a brand new character as a consequence.
Also, Bashiok notes that the system that will be put in place for Diablo 3 will not be identical to the World of Warcraft respec system, and players will not be able to respec their characters so liberally.
“There will almost definitely be some sort of system to respec; however, it isn’t likely to be as liberal as World of Warcraft. We don’t want to lock a player into a system that punishes them for mistakes, experimenting, or lack of knowledge early on in the game. We also don’t think a system that allows immediate, complete, and at-a-whim changes to a character spec matches the feel of Diablo. It’s likely to be somewhere in between.
That said we still feel like the desire to play the same class again that you may have played before is still a part of the game, and with some ability to respec could potentially require other incentives. “