Brando and I do a lot of online fighting game matches and if one person has a bad internet connection it can actually delay things on their end. So for example if I have a strong connection and I perform a move it will end up delayed on their end and they will be reacting with a delay. So it ends up effecting both ends. It's like one person is playing waist deep in mud.
I think it's a generally valid upset, not that it's some big serious issue to me personally but it can really effect a match and sometimes the person on the slower connection isn't really aware how badly that can change things for the person on the other end too.