Is it just a fun prank or hateful crime? My personal opinion is that it depends on your intent and the level in which you TP them. Also the personality of the person you are TPing. For instance if you just use toilet paper on the house and the person is someone who has TPed before or TPed you, I feel it is a fun activity. If you use other things such as eggs and things that vandalize and you TP someone who doesn't like it, it is mean spirited and you should not do it.