Regina Buenaobra of ArenaNet, "Hey everyone, I have an update regarding the availability of raids. Due to the issues we experienced yesterday with the Enhance Squad UI and with further internal discussion, we have made the very difficult decision to keep raids turned off for the remainder of the beta weekend. We are continuing to investigate the issues and also looking into options that would allow us to get more testing on these features before we release. We thank you for your patience and understanding."
Update: Nova said raids are working for him 10/04. I was able to enter a couple raids on 10/04 as well.