Rating: 5 / 5
I could have had to hike in these when my Montrail GTX's blew out, and probably could have done it until I wore the bottoms off. The nice thing about CROCS is that they are very comfortable, relatively lightweight (13 oz for a Mens size 12-13).
They're very comfortable slip-on with a flip up strap. The only down side is they are a little price, typically $40 a pair. There is a very similar pair available, with slightly stiffer foam available for about 1/2 the price at WalMart, but try both out, as some people like the firmer "Wallies", and others like the softer CROCS.
In all seriousness, I don't think the soft material they're made of would last a 20 mile hike, but I expect you could make miles if you had to.