For illustrations of potential end-user downsides of SOPA and ProtectIP/PIPA, and to do something about them (yes, you), see..

GetYourCensorOn
http://getyourcensoron.com/

Stop American Censorship
http://americancensorship.org/

For what a bunch of folks involved in engineering the Internet think, see..

An Open Letter From Internet Engineers to the U.S. Congress
December 15, 2011 | By Parker Higgins and Peter Eckersley
https://www.eff.org/deeplinks/2011/12/internet-inventors-warn-against-sopa-and-pipa

For some further commentary, see the below (this is just some highlights, you don’t have to look far to find a bunch more out there)..

Some Data On How Much The Big Media Firms Are Donating To SOPA/PIPA Sponsors
http://www.techdirt.com/articles/20111203/00494716961/some-data-how-much-big-media-firms-are-donating-to-sopapipa-sponsors.shtml

YouTube rejects UMG demand – Megaupload Mega Song returns
http://www.nnsquad.org/archives/nnsquad/msg06203.html

SOPA-Rope-a-dope (by Stewart Baker)
http://volokh.com/2011/12/14/sopa-rope-a-dope/

Technical Comments on Mandated DNS Filtering Requirements of H. R. 3261 (“SOPA”)
http://www.circleid.com/posts/20111211_technical_comments_on_mandated_dns_filtering_requirements_sopa/