Some enterprising hackers have successfully created 128-player servers for the Battlefield 3 Beta. Players using the Beta are only supposed to have access to the 32-player Operation Metro map in Rush mode. However, some servers have been appearing offering the Metro map in Conquest mode... with 128-player support.
According to Battlefield 3 Blog, these servers have been "considerably laggy". EA has since released a statement on Battlelog, informing players not to join any hacked servers, or they will risk losing their EA accounts.