There are security concerns associated with cross-realm raids. Posting Battle.net emails on the forum is a pretty bad idea from a security standpoint, and we don't really want to encourage it by having a forum dedicated to that sort of thing. Beyond that, there may be issues with scams and ninjaing, and we really don't want to help those who would abuse the system.
I'm not saying it will never happen; we just need to figure out a way around these issues first.