This was the method I was thinking of myself, because as with another idea posted in the forums, if it's quest related to unlock chat features, it won't take long and the RMTers will just do it anyways. They have the time, obviously, it's all the do, all day everyday.
If we could just toggle who could send us /tells, it'd free up a lot of annoyances and interruptions. While it doesn't get rid of it altogether, it will at least lessen the amount.
The friend requests though... Harder to get rid of, but from what I understand with 3.0 trial accounts aren't supposed to be able to send them anymore? At least, that's what someone told me, but I've still been getting them.