[Steve_Seattle]

"It seems to make sense if a person posts opinions online but has no mention of where they work . . . "

You're ceding too much ground, IMHO. Even if someone doesn't mention their employer on Facebook, somebody else could point that out, and you'd still be screwed. So before long conservative opinions would be entirely self-censored from Facebook. Bye bye, free speech.

[Secret Agent Man]

Many people post under screen names and people do not know who they are.