what constitutes hitting n running??

[Schneids]

Regarding #1, my personal take is if you get past the 2 hands played stage of HU (ie the game was fuller and then ended up just you and him, and then you each play the button once and neither of you quit after that), it is implied you are agreeing to sit and play HU for awhile. To me, it is poor etiquette to simply quit as you did, unless you had said near the beginning "I'm not going to play for long" and your opponent is aware you might be quitting. Or lets say you get down $2000, and decide in your head "If I win that back I'm quitting," I believe the proper thing to do is to tell your opponent "If I get even, I'm done." I have done this a few times, and usually my opponents take it positively and continue playing anyway and appreciate the warning. As it is, once a HU match has "begun," I think the only way it should ever quit is if one opponent gives at least a 15 minute warning of when he plans to quit. I know many who disagree with me on this view though.

#2 is totally legit IMO, if he doesn't want to play the other opponent that's his choice, but he at least has a chance to "get unstuck."