Whatever version is eventually passed, abuses are possible. There will be sites that will take the safest route, do anything to avoid being on the wrong side of the law. And there will be people and companies taking advantage of that.

Some of it already goes on. eBay, for example, has had rules in place for years that require a auction to be canceled, and the seller to possibly lose his rights to sell on eBay, if someone complains that the auction infringes on their copyright or intellectual property. eBay has a list of registered companies and individuals. If one of them fills out a form claiming such-and-such auction infringes on a copyright, eBay kills the auction. No investigation. None. The safest, most expeditious method of dealing with such claims is to automatically follow the copyright-holder's wishes, even if that person or company merely doesn't like the idea of someone selling their product without being an authorized reseller charging a determined price. Some software companies, for example, have a group of people watching for instances of the product being sold or resold. Some of those people even have the company's proxy to file a complaint and get the auction shut down. I know, because once upon a time I did it.

That's eBay. It's easy to imagine other kinds of host providers following that logic. Who has time to investigate claims and get tangled up in legal fights? Take the path of least resistance and shut down the allegedly offending site. Again, people can take advantage and game the system for their own purposes, ranging from competitve advantage to plain ol' spite (the site banned you for being a persistent and annoying troll, for example). 

I certainly don't advocate letting the pirates and hackers do whatever they want without fear of consequence. Nor can I think of a way to keep any such system from being abused, or from trampling on innocent people's rights. So I think we have to swallow a bitter pill to get piracy under control, but at least let's make it the smallest pill possible. The original version of the SOPA bill went overboard.