This from the official Playstation blog, which was posted sometime yesterday:
Killzone fans! We know you are eager to join the Killzone 3 Multiplayer Open Beta and the team at Guerrilla Games has been hard at work finalizing the content. The good news is that the beta is looking better than ever and we can’t wait for you to try for yourself. Unfortunately, we’re here to report that we will have a slight delay on the beta availability. The open beta was originally set to begin on Wednesday, February 2nd, but will now be available on Thursday, February 3rd at 10:00 AM Pacific Standard Time.
To help make up for the date push, they're giving away 60 Killzone 3 Limited Helghast Editions (not sold in stores) to players who participate in the Open Beta this weekend. The Limited Helghast Edition contains all the same elements as the retail version of the Helghast Edition, but features a Helghast Helmet replica with illuminated LED eyes (simulating Helghasts' glowing mask). They're only making 1,000 of them, so they truly are "Limited."
Log on and play the Killzone 3 Multiplayer Open Beta from Friday, February 4th through Sunday, February 6th. They will be randomly selecting 20 participants each day who are playing in the Open Beta and notify winners via the email address associated with each entrant's PSN account between February 10th, 2011 and February 18th, 2011. Check out the full rules
here.