I'd lose all my information and it would end up somewhere on the internet or someone's hard drive getting ready to go up on there. My family could be threatened or my job could be at risk because of political opinion I have. If I bought a toy for my son on Amazon and typed in my credit card number someone would eventually have access to it either in couple of years or just a couple of seconds.
The third issue what I do, on my property, with my computer is my business. If I wanted to tell the world that I ordered a giant bunny suit, I'd get in my car, go to Party Planet, and buy a bunny suit, but for some reason I didn't (If I did buy a bunny suit). That's the problem though, what I do is my business, not my internet provider, not the leech trying to hack the internet provider, my business. Any gifts I bought as a secret someone would know, any movies or music I listen to, people would know. It's weird and really creepy.
In the end it's a really stupid question to even ask me and if my internet provider made me sign it I would dump them instantly. People may to spin this on criminals and trying to catch them but I know I haven't done anything wrong so why should I have to face the same fate as them? It's a dumb idea, even dumber execution and personally I think anyone that agrees to this is asking to have their information on the internet. Though everyone has different values and some may value to get cheaper or better internet than to have