If your opponent's computer loses its connection one in a million times, then you can say you are playing for that possibility to win !
Personally, I see that as low class and would instead resign.
Same rationale as playing in a tournament thinking about resigning in a dead lost position, with otherwise no hope -- ie; my opponent can have a heart attack and die or he/she can be called away for an emergency.
I run into this a lot in arenas so I thought I'd ask about it. Let's say there are 30 seconds left in an arena and I have 35 seconds on my clock and my opponent has mate in 1. Is it proper chess etiquette to just let my time run since the arena will end and thus abort the game before it is over? I know it's allowed, but I'm not sure if it's proper.