I would say that what work against SOPA was big names like Google and Wikipedia weighing in on the matter.

If the internet population wasn't behind it, I don't think Google or Wikipedia would matter much.

The noise generated on Twitter and Facebook made politicians take a closer look on SOPA and companies voice their opposition to it.

I don't think that Google and Wikipedia used the number of signatures on the petition on whitehouse.gov as a major component in their decisions to come out against SOPA.