Many of these really egregious bills are unpopular with the majority of americans, but their opinions are not represented by the actions of government. There's little they can do to get real reformers elected because the "two party" system focuses on immaterial differences between the parties and on these issues the parties are pretty close. Most democrats and republicans voted for the PATRIOT ACT (and its renewal and extension under Obama) as well as NDAA, etc.
I'd love for someone to find a way to make democracy work. If there were a way to keep the US government constrained to the powers enumerated for it by the constitution, then we wouldn't have these problems.
But the only "checks and balances" on the government are all part of the government, and thus have long ago been compromised, there's no real oversight.
That's the fundamental problem.
If SOPA is "defeated" it will just rise up under another name in a few months.
SOPA itself is only the latest attempt to do this- they've been attempting to gain this level of control over the internet using the excuse of fighting terrorism for several years now.