It appears one of the guys over at The Defaced Security Team have got their hands on the files needed to host your own Battlefield 3 beta server. Initial reports suggest it is possible to have a server hosted on your PC listed on the master server list accessible by anyone. Two servers have currently been spotted; one such server showing as many as 128 player slots. Whilst many fans of Battlefield had been annoyed at the exclusion of Caspian Border, the leaked files unfortunately do not include the Caspian Border map and is therefore unlikely to excite the majority of Battlefield players.
http://forums.electronicarts.co.uk/battlefield-3/1434597-battlefield-3-beta-server-files-leaked-defaced-security-team.html