As a writer, I believe the current message ("The Wikipedia community has authorized...") is long and wordy and therefore not likely to be read by most users. I recommend shortening & simplifying it. Here's an example that removes 30+ words and preserves the meaning:
WE NEED YOU TO PROTECT FREE SPEECH ONLINE The English Wikipedia is "blacked out" for 24 hours to protest two bills before the United States Congress, known as SOPA and PIPA. These bills endanger free speech in the United States and abroad, setting a frightening precedent of Internet censorship for the world.
Today we ask you to take action. [[Take action]] [[Learn more]]
Just a suggestion. DanB