There is a powerful lobby behind these bills, and many in Congress are sympathetic to the lobbying industries and/or do not have technical backgrounds to understand the greater effects the bill will have. I think that both Congress and the industries behind these bills were surprised to see such resistance. In addition to blocking bad legislation, IMHO this protest is a good thing because: 1) It sets a precedent that some aspects of an open internet will be vigorously defended, and 2) it further demonstrates how people can use the internet to organize and pressure their government. A very real concern is the effect that SOPA/PIPA would have upon sites that facilitate this kind of organization. Personally, I doubt that we would have this large scale protest if Reddit didn't exist.