Blizzard is firmly on the side of those that see it as good. In a recent blue post Bornakk has came out and said that while the option is there, they have no plans to allow it. Apparently this has "been on the table" for the past two years.
Personally, I'm glad they won't be allowing this. The ability to transfer from PvP to PvE makes sense since you won't be disrupting the gearing balance. But think about what would happen if you could transfer from a PvE to a PvP server. Everyone would level their characters on a PvE server, and then transfer them to a PvP server at 70. This would make it nearly impossible to get a group or have any pre-70 game play on the PvP server. I know some of you are going to say that it already is impossible, but it would just become more difficult. So I'm with Blizzard on this one.
What do you think? Is it a good policy, or should Blizzard change their ways?