Now that is nice.
It can be extended to trails on certain kind of land, like for example when there is thick grass.
I believe for it too make sense, the server would need to record trails and let them fade out after a while. In addition to having the effect. I think that would be quite some work.
I really like the notion of this as it would mean that at least temporarily, characters leave a mark on the landscape.
But imagine a GM event where there would be real trails to follow some bad guy. That would be nice.