Call me stingy, but I very rarely give out buffs for nothing. My main is a shaman and it gets very annoying and hard on the mana to keep casting Focus to every joe who wants it.
If someone asks me if I can buff them I usually ask if they will donate... that gets me some smart *** comment most of the time, then I just go on my way. It's no skin of my teeth if I don't get to buff you.
That being said, some people who want the buffs will send me a tell asking for them, and tell me right away that they'll donate. At least they make it worth my time and mana.