There are lots of breathless claims all over the Internet about the degree to which these bills will cause harm to the Internet, just as there were with DMCA before them. Indeed, people are talking about how any site might be taken down without notice, how payment providers and advertising networks might be forced to stop providing revenue streams and so on and so forth.
Most of these complaints are from people who have not bothered to read the full text of the bills, and are really just parroting what they have heard elsewhere. The result is that while they may be aware that SOPA could in principle be used to take down a site, they are unaware of the conditions attached to this, namely that:
The owner or operator must be committing or facilitating the commission of criminal violations under sections 2318, 2319, 2319A, 2319B or 2320, or chapter 90 of title 18 USC.
The site would be subject to seizure in the United States as a result of these violations if its owners or operators were located in the United States.
That is, in order for a site to be subject to take-down, it must already be breaking United States copyright law, and it would already be subject to take-down if its owners and/or operators were in U.S. territory. So, really, this part is just extending existing provisions in U.S. law so that they apply where the domain registrant is overseas. That seems fair enough, frankly, particularly as U.S. registrants might otherwise pretend to be overseas to escape the existing legislation.
Another thing that SOPA and PIPA do that is causing consternation is that they provide a mechanism for those whose rights are being infringed to notify payment processors and advertising networks that they must not process transactions for or make payments to the alleged infringer. This requires a notice similar to the ones specified by DMCA, and, just like DMCA, it is possible for the affected site to file a counter notice. And just like DMCA, if a counter notice is filed, it is the courts that must be used to decide what happens next.
They also create a limited immunity for anyone acting voluntarily to prevent copyright infringment; potential liability to their own customers has been used an excuse, historically, by registrars, payment processors and others, for continuing to allow their customers to egregiously infringe others’ rights even when their own Terms of Service explicitly ban such behaviour.
There have been all kinds of claims about the technical consequences of SOPA and PIPA, though most of these have been (as far as I can tell) baseless, since neither act makes any kind of stipulation about the technical measures that may or may not be used in its enforcement. I tend to think these are really a case of special pleading from a group of people who are making not inconsiderable sums of money from other peoples’ copyright infringement and/or are worried that enforcement might create additional costs for their businesses. These are not disinterested parties.
Anyway, regardless of your views on SOPA or PIPA, the blackout by Wikipedia is childish, affects countries other than the United States, whose citizens have no say whatsoever in whether or not the U.S. Congress or Senate pass their respective bills, and in addition has been done in a half-assed way.
For anyone who wishes to browse Wikipedia with Safari today, here’s a Safari extension that undoes the blackout.