Unless you are cutting down trees or building a road, you don't need to use flagging tape. If you are worried about getting lost, a GPS, or dare I say, a map and compass (!) will work just fine.
In general there are situations where a marker is very useful, where the route changes direction or to show a less technically difficult route, What do you do when you hit a cliff band on the way back down and can't remember how you got up it?
On this occasion the tape wasn't really necessary, the terrain easier than expected, but why take chances?, i'll more than likely do the route again and remove the tape.
I don't really like the idea of GPS, what happens when it fails?