Massively reports that Blizzard has reversed their earlier stance on no PvE to PvP server transfers. Per Bornakk on the official World of Warcraft forums, Blizzard has decided to open up transfers from PvE servers to PvP servers because "World of Warcraft has matured significantly since the inception of Paid Character Transfers, [they] don't feel that PvE-to-PvP transfers will have the negative impact on the game that [they] initially wanted to avoid when [they] started the service in 2006. This change will provide more mobility and freedom for players to experience the game with friends or play in the type of environment they're looking for."
