I'll delete if I accept the challenge in like a 1/na game and the person starts out slow as heck. Can only play 6 at a time for the moment so i like to finish games as quickly as possible.
Anyone who does that is a real jerk.
They usually spout some rubbish about accepting and then looking at your profile and changing their minds. They should lose rating points.
I have a bunch of them on my timewasters list.