Interestingly, Mel B's approach is far closer to the 'real' audition process than that portrayed by the other judges.
In a real audition situation, the majority of people wouldn't get as far as standing on the X - they'd be walking off the way they walked on without breaking step because they don't look right, so how they sound would be irrelavent.
There are exceptions to this rule - the most obvious of course being Susan Boyle - but as a rule, people who don't look like pop stars will not become pop stars - Alexandra Burke against Michelle McManus illustrates that point perfectly.
After about three or four seconds, a lot of auditions are over, because that is how long it takes so see if anyone is going to have a chance of getting anywhere - but of course, that is not good television.
I imagine there will be more 'hopefuls' as the weeks unfold - there is no major pull for viewers in the early weeks without them.