But I also think that a call to action is even more important, so hopefully they don't just go offline, but present the visitors with an overlay or a widget or something to call their representatives, and with some clear explanation in layman terms of what SOPA and PIPA do.
"If these companies were to take this route, all of these sites would go completely dark save for a message of opposition to SOPA censorship and instructions on how to contact your local representative."
If web giants -- those that are used most by those unaware or uneducated about SOPA -- were to post a page about SOPA in place of their services, people would have no choice but to take notice and learn what "this SOPA" is all about.
My (and many people's) individual words will not have near the impact that seeing giant organizations cooperatively taking action -- by giving up a day's worth of business -- in opposition to something.
That's not to say that we shouldn't try to educate others. But something like this will go so much further -- it will hit deeper and broader.
I even heard that people in IT have said that other people they work with have no idea about the ramifications of SOPA and many other anti-Internet bills.