How about going to a manager - thats what they are there for. They get the extra bucks to do and say things you don't want to! If the manager is unwilling to help, go higher. You definately don't have to listen to that all day long.

If nobody is willing to help... then how about leaving an annonymous note on their desk chair after they leave (or before they arrive in the morning) asking them to please consider the others before they sniff their snot. Tell them how distracting it is, and how simply blowing their noses would be much preferred.

PS: I never hear the term snarf before either!