I don't generally care if somebody needs a pull as long as I know somebody is behind me. I also have no problem drafting off of somebody who is willing to pull me. Usually if I need the help of a pull I ask the strongest and fastest cyclist I can find as they pass me. I have once or twice asked a stranger to pace me back up to my group.
I also feel that every cyclist should know how to defend their front wheel.. More importantly have had the opportunity to try it. I hit my wheel once on the back of a friend and turned in properly and pulled away while staying up. Turns out I ended up needing that ability is a race the next week. Somebody cut in to soon around me.
Generally it seems frowned upon to draft or pull somebody you don't know.