Twitter didn't go dark to protest SOPA / PIPA on Wednesday, although some thought they should. An argument against Twitter shutting off its service was that it would severely hamper the flow of information about the other SOPA Blackouts. Basically, "where are we going to talk about SOPA and PIPA if social networks shut down?"
On that note, Twitter said that from the moment Wikipedia went dark to 4 pm on Wednesday, there were over 2.4 million SOPA-related tweets making their way through the Twitterverse.
Probably the most amusing top term was #factswithoutwikipedia, a hashtag trend that lasted nearly all day. People did their best to make up ridiculous facts that might exist if we didn't have Wikipedia readily available.
The SOPA blackout was also a success using another metric. Google announced that 4.5 million people signed their SOPA petition featured on their homepage yesterday.