I'm in favor
Although there are slightly different considerations on a Flex Mobile project than a Flex web project, they are still Flex projects; and most of the content would be similar.
Would you also ask for a Flex & AIR forum vs a Flex Web forum? Probably not.
May be we need a diferents forums about target platform:
Flex for Flash Player
Flex for AIR
Although it will be difficul find post of mobile in flex forum (in Air forum is very easy because its separated)...