I think a year or 2 ago there was a discussion here about Wynn
scanning peoples licenses as part of the slot card sign up. I recall
that one could ask them not to do this, but I do not remember if we
had a legal right to refuse it.
I found that at the Venetian, in cashing a $15 cash back check, that
they took my license to scan. When I protested, saying it shouldn't
be necessary, the cage supervisor, (get this one) told me it was due
to 9/11. He claimed if the check was for $1 they would do the same.
I guess they must have found that bin laden was funding terrorism via
slot cash back. 
Does anyone know if there is any legal protection that would prevent
them from withholding cash back from someone who will supply their ID,
but refuses to let them scan it? Do they have to honor a request to
not scan an ID that was handed to them?