I would be very surprised if the Marshall Service doesn't have pretty straightforward guidelines about what sorts of things to avoid when under witness protecti

I would be very surprised if the Marshall Service doesn't have pretty straightforward guidelines about what sorts of things to avoid when under witness protection. I would expect that having a Facebook account at all is something to avoid. I can see a situation where eventually the idea of not having a Facebook account is in itself something unusual, in which case they might need to refine the policy, but I suspect that currently, it boils down to "don't use Facebook, don't use Twitter".