A former Blizzard employee (kidr3volver on Reddit) has posted screenshots (and now a video) of the Diablo 3 beta.

Source of the information can be found here.

His IMGUR album is located here. And you can watch the Beta Player Character Screen video here.
ForceStrategy Gaming called it all fake photoshop work, but it looks pretty real to me. :)

According to his IAMA, "the majority of my life in blizzard was under the account and billing/tech department but have some general GM experience as well".

I don't think kidr3volver was too serious about protecting his identity though. According to previous Reddit posts, he publicly revealed his name and date of birth: Joshua Shields, 1986 (jshields1986). According to his public Google+ profile, he worked for Blizzard Entertainment in the Account and Tech Services department from 2010-2011.

Here's his LinkedIn Profile and a screenshot and here's my favorite part:

Learn and review departmental policies and procedures.
Maintain security and confidentiality of Blizzard Entertainment internal information and customer/account.

He probably received an earlier beta invite through the "Friends & Family Members" closed beta invite, considering that he's not currently employed by Blizzard.

His jshields1986 unique alias is all over the internet as well, and there are plenty of pictures of both him and his cat.

http://cheezburger.com/jshields1986/
http://www.quickmeme.com/user/jshields1986/oldest/
http://s634.photobucket.com/albums/uu64/jshields1986/
http://imgur.com/user/jshields1986
http://www.resumebucket.com/jshields
jshields1986@gmail.com, jshields1986@yahoo.com, etc. etc.

This is a really good example (and a warning) of how important it is to protect your identity and "internet footprint". Information about you is all over the web, and it just takes one slip up to link all of your aliases to one identity.

Unless this is all an elaborate conspiracy where someone borrowed this persons alias in an attempt to frame them. For example, he worked with Joshua at Blizzard, didn't like him, and now it's payback time. :)

** Update:

Kidr3volver has been going through and deleting all of his Reddit posts. I wouldn't be surprised if he pulled the images and YouTube video too. (It's already been reposted though.)

And, Blizzard has just deleted one of the Diablo 3 discussions on Battle.net. Never had a chance to read the entire thing and it was up for about 5-6 hours.

Here's the one that was deleted: http://us.battle.net/d3/en/forum/topic/3118271920

Interestingly enough, they still kept the original older posting (7 hours old now) that contains all of the personal information about the leaker: http://us.battle.net/d3/en/forum/topic/3118161991

I had thought it was against B.Net forum rules to post that sort of stuff there. I wonder why they deleted the newer post, but not the original?

It might have had something to do with the comments made by Sixen on the forum (he's a Community MVP.) They were talking about favoritism (i.e. friends that hooked them up with invites) for Beta selection: [Image 1] [Image 2] [Image 3]

Sixen was also originally telling everyone that there was no Diablo 3 Friends and Family "F&F" Alpha/Beta, then changed his tune when corrected by forum users:

"There will not be a Friends and Family Alpha or Beta. The game is going right from Internal Alpha to Public Beta."
"Nevermind, apparently I'm wrong, there will be an F&F."
"Nope, the info I had changed."

** Update:

Confirmed; he just pulled his YouTube video.

There's another copy here for your viewing pleasure.