I don't think many would actually use it. But for those that bitch and bitch and bitch about certain posters.....the option could always be thrown in their face to get them to shut up and quit whining.
When only a few folks use a certain feature, then why implement it? Two many of those features will kill the user friendliness of this forum.
If someone is bitching about you, then simply start a constructive PM discussion with that person. If that doesn't work, you can always ask a mod for assistance.
Denying folks is for whining bitches and remember, this is fucking Getbig!