The field I've been playing at has a 10' surrender rule.
If I really sneak up and scare someone I'll try to surrender them. I prefer to give myself away and shoot from further back though. I usually shoot at 15'+ whenever possible; I've never had someone complain about a single shot, even if it's in the back, from 10 ft+ (we're usually chronoed down to 260-270 though). I have however, had bad experiences shooting/getting shot at close range (~3-5 ft) when trying to surrender people closer in (they usually panic and start shooting). If it's obviously a newer player I always either put myself in a position to shoot from further away (they're easy to flank) or just snap shoot until I get them.