In the wake of yesterday's rumor that the Cataclysm Friends and Family alpha will be starting this Tuesday, January 12, we should expect an increase in scammers trying to get your account details by offering phony alpha invites. We saw a lot of these for both Burning Crusade and Wrath of the Lich King as well, and some of them were very well crafted.
At this phase of Cataclysm's development, though, it will be comparatively easy to keep yourself safe. Since this is a friends and family alpha, if you don't have friends or family that work at Blizzard, you will not get an invite. Therefore, anyone offering you one is trying to pull a scam. Basically, everyone who's going to be getting legitimate access to the alpha should know who they are already. Everyone else, sit tight and stay tuned to WoW.com for the latest on WoW's next chapter.
World of Warcraft: Cataclysm will destroy Azeroth as we know it. Nothing will be the same. In WoW.com's Guide to Cataclysm you can find out everything you need to know about WoW's third expansion. From Goblins and Worgens to Mastery and Guild changes, it's all there for your cataclysmic enjoyment.