Im not in favor of neither but both provide/develop/etc basically software, if this (SOPA/PIPA/whatever) affect to their sells (which in this case is not) they for sure will do something. You could say that Bing or Yahoo will be in the same situation that google or any other crawler are but they are not. Bing is not a priority (by now) for microsoft, they are selling every day and in every opportunity their next and super flexible OS (dont make me start talking about the BIOS thing because thats another "war") instead worring about some freedom/copyrights thing.
It's funny how Apple didn't do any action to raise awareness to this issue. Neither did Microsoft. We can clearly see now which companies are really working to protect the internet and which ones are the ones who are just silent on the issue as they initially supported SOPA/PIPA (Apple, Microsoft etc) and are like weasels now not putting their support in protecting our internet freedoms.