Clay Shirky elegantly explains the most chilling aspect of SOPA/PIPA:

“The scary bit of legalese here is the idea that the law would apply not just to actual copyright violations (the nominal goal of the law) but to any site that was “facilitating the activities” of copyright infringement, a term nowhere defined but vague enough to include mentioning the existence of such sites, which is enough to make them findable. Like a fast-spreading virus, the proposed censorship moves outwards from the domain name system, to include any source of public web content in the US.

“If the phrase “any source of public web content” seems like a dry detail, substitute the name of your favourite web publisher: you.”
http://www.guardian.co.uk/commentisfree/cifamerica/2012/jan/18/sopa-pipa-consumption-only-internet?CMP=twt_gu