The first salvo of invites appear to be limited to those who signed up for the Crysis 2 community site. In August, Crytek and EA detailed the beta, which was to include two modes: "Crash Site"--a capture and hold gametype--and "Team Instant Action"--a standard team deathmatch offering.
The email details the beta as a "tech test" and reaffirms that it is Xbox 360 only "this time around". Let us know if you've received an invite in the comments.
There are 2304923480923840923798 rotten corpses in the ground, including your grandmother.
The answer is the consoles hold back the PC. Since we don't have PC exclusive titles like Crysis being released very oft...