USA TODAY - The Super Bowl halftime show might have been the biggest air guitar display in music history: http://usat.ly/1endrTU.
As noted by Fansided, Red Hot Chili Peppers bassist Flea and guitarist Josh Klinghoffer didn't appear to have their instruments plugged in during the halftime show, which came during the most-watched television program of all time: http://usat.ly/1gJrlBB.
In a picture from a 2011 concert, you can see a cord at the bottom of Flea's bass: http://usat.ly/Lvd3WB. A close-up of that picture shows the cord runs from the instrument's output jack to something in the back of the bass, presumably a wireless pack: http://usat.ly/1k7SWgj.
In January, Flea played the national anthem before a UCLA game. His bass is clearly connected to a speaker: http://usat.ly/1ev4WVn.
Here's Klinghoffer playing guitar during the Super Bowl performance: http://usat.ly/1nO0hlo.
And here he is at a show in Paraguay last November. Notice the cord: http://usat.ly/1ipqhAn.
Though there's been no explanation yet, it's possible the band was concerned about playing stringed instruments in cold weather. In 2009, renowned musicians Yo Yo Ma and Itzhak Perlman didn't play live at President Obama's second inauguration due to the frigid temperatures. (The cold can warp the sound: http://usat.ly/1jbAPG6).
Whatever the reason, it's interesting that musicians like Yo Yo Ma and the Red Hot Chili Peppers skate for their instrumental lip-synchs. On the other hand, when singers do it, we raise the pitchforks: http://usat.ly/1lyDs6E.
To his credit, Bruno Mars appeared to be singing the whole time: http://usat.ly/1eQt0P7.