I have in several cases, resharpened and periodically maintained the edges of knives that I have given people.
If I have close friends or family members that I have given a knife to, or who just have knives they already have used and carried on their own, I will sharpen it for them once in awhile. I find that people get so used to using dull knives (really dull by our standards) that they don't even realize their knife could be sharper. Every time I resharpen one that was really dull, and return it, the look on their faces is well worth the time to sharpen! They get that "Holy #%*@" look, and you can see them thinking, "Dang, is this thing still safe for me to use?" I'll remind them to slow down and be careful, that most cuts shouldn't take too much force.
It could get out of control quickly if you've given away lots of knives to a lot of different people.