Hmmm...
I've never had it happen - however, if I ever engaged in sexual intercourse in which another man was involved - it's sort of expected that there is a real possibility of coming in contact with his, ahem, cum.
Let's face it, you both are sharing the (probably) very wet orifice of a woman. If there are no condoms present, you are definitely coming in contact with each others precum and other such fluids that are secreted. So I personally don't see what the big deal is.
Simba