I think this will certainly become an issue as more teams start using wifiLapper at the track.
However, if pitside goes multi-car the issue won't be with corruption of the data-stream.
It will have more to do with access to information you may not want teams to know (either out of strategy or embarrassment) and resources (disk space, bandwidth, etc.).
Either way, some sort of simple security would be a good thing to have. I think encryption and/or key sharing might be overkill, though.