Can we target Facebook ads by someone's surname?

Highly unlikely. Targeting seems to be mainly by age, gender, and location.

Being ignorant of such things jes, why would this be impossible, or even hard or unlikely?

If you are able to tell a persons gender or age, why couldn't you have a data base of certain names, and target them?

It's what FB provides. Of course it would technically be possible if FB provided the information to page runners. But it doesn't. Part of that is user privacy, BTW, but it's also because of how enormous the database really is. There are 1.3 billion accounts on FB. Aggregating gender, age groups (they don't aggregate actual ages, I might add) and generalized locations - all of that stuff is provided. This is essentially what's provided to advertisers. But surnames aren't provided.

Ah.

I see.