How would you know? If you're both asleep, how do you know your snore buddy is actually snoring? Unless you alternately wake each other up with the snoring, which just sounds like a miserable night's sleep all around.
Also Tdol's last comment reminded me of another buddy term I've heard: f*ck buddy. Maybe that's what a snore buddy is, but instead of carnal delights, it's auditory delights.