I've also gotten a few of the RMT friend requests and I don't understand what they hope to accomplish.
Basically, when they send a tell to a player, there are two possibilities: Either the player is interested in their services or not.
For players NOT interested in their services, all they are doing is making it slightly more annoying to blacklist them---we'll definitely still do it. But making their messages more annoying seems counterproductive---the more annoying they are, the more we will complain to SE and they will try to do more to throttle them.
And for players who ARE interested, it seems like an even worse idea. Again, just because you might want to buy gold doesn't mean that you want that bot on your friendslist. So interested players have to go through the hassle of declining the friendlist invitation as well. Now they're also annoying their potential customers.
I don't see the point.