I've given away many quilts but for the ones I gave to my grandchildren I did let them know their graduation quilts should be treated with respect. I've given them "car quilts" they can do as they wish with, but the special quilts are just that. Now, granted, I can say that to my grandchildren. I probably wouldn't say it to a friend.
I like the remarks of the lady who said by using the quilt, they were really saying it is special. I have a favorite quilt I use as a chair throw and I just feel good everytime I sit in that chair. Perhaps your friend feels that way when he lays on your quilt. (I hope it is very washable!)
Having them use it beats your kids selling it for 5 bucks when you are gone. :>