I don't know about anybody else but I have written shareware in the past so I have this thing about registering everything I use.
Also I'm already in the porn business so when they come in and raid me I like to have everything legit.
Call me paranoid but thats the way it is.
Besides if you like a product and you register it that mean the company that made it has more money to develop better products.
Also software is a good write off. My account loves software reciepts
