Rally racing is the only interactive racing. I don't know of any other racing were people help the drives when they spin or ditch the car. Rally fans are a little crazy though.
There was one time (not sure about the rally, acropolis maybe, but it happened this season), where a wheel came off the car and started rolling away and the fans just watched it.
I've seen rallies a couple years ago where fans moved the directional barriers to send a perticular driver off course. Not into danger, or anything, but off the stage to ruin his time. That was crappy behaviour.