I loved that - I don't care if he's danced before, I just love watching him and Aliona dance. (The fact that he looks a bit like my son helps
)
I would guess that each year they have to have a few who have some sort of experience anyway - otherwise they could potentially end up with a floor full of the rhythmically challenged.
I think anyone who has performance experience has an advantage anyway - and you can't rule out all the actors because of that.
I feel a bit sorry for Katie - I hope Anton gives her something next week that will show off her ability.