Take an application for an example, you don't want to BS it because you are trying to sell yourself out. You want to put time, and effort into what you say so you have a better chance of getting hired. (Or in a WoW scenario, you get accepted to Raid/PvP)
I feel that the more you put effort into a request, as in not just saying "I want a signature", but a well thought out request showing how much you really want it done.
Just my two cents.
(Sadly still doesn't stop those people who PM multiple artists.)