For starters I have never played the game (Buy Diablo 3 from Amazon if you’re interested!) and hence have no online account but if you are somebody who does play it, this could easily suck you in!
No attachment on the email which is good, but as usual do not click through on the link in the email (it does NOT take you to an official us.battle.net page) – you’ll be filling in a form with your details heading to goodness knows whom!
(click on this thumbnail image to see a screenshot of the email)