That sounds like a lot of fun.
For it to work though.. you'd need to let everyone know in advance, and I'd make it so there is maybe.. I dunno.. a two hour slot of time.
Of course, you'd have to make some type of crazy recommendation... or who knows.. maybe an "instant remix" contest.. where we find an artist willing to donate a sample or acapella to the project.. and then when you say go, you post a DL link and people just go for it, and upload by the deadline.
Then, have a few judges ready to blow through all the entries within 2 hours...
And follow it up by a results broadcast almost immediately after.
So like a 5 hour turnaround time for the whole contest.