I would imagine if you are stupid enough to perform outside your companies SOP's willfully knowing 'big brother' is watching via FDM, which then accumilates into some kind of incident you will/can be sacked!
Although FDM itself isn't supposed to be used as a HR spy, it will and can incriminate you. Flight Safety is first and foremost, thus we shouldn't be affraid of FDM - the opposite, we should use it as a training/learning tool.
As for the legal aspects of FDM, I can only summise that if an event has occured which has been captured on FDM and d'management deemed it gross missconduct, the crew involved may have a bit of a legal battle on their hands!