Or whom they're pretending to be? Remember, this is the internet, so a claim of gender (or locale) is considerably less trustworthy than using the Mick Dundee method.

Of course, since you're not likely to ever meet ftf, it's simply polite to treat people as if they were the people they claim to be. Who does it hurt?

(ftf=face to face. Now there's an abbreviation that's been around since before DarpaNet, back in the old days of hardcopy personal ads.)