Check your inboxes! Select Dead Space 2 fans have been "hand selected" for a closed multiplayer beta. Scott Probst, Multiplayer Producer, explains in the invite e-mail: "We have just launched a small beta which will help us polish the game, and we have selected you to help us achieve that goal! We are still several months away from the game's release, and there is still plenty of work to be done prior to shipping the game." In addition to a PSN voucher, the invite e-mail includes a link to a forum for participants to offer feedback.
Unfortunately, the e-mail doesn't detail how participants were selected. The invites appear to be targeted to members of EA's online community, with no regards to PlayStation Plus. We'll update this post if EA can offer us any more details.