Don't you think you're looking at this the wrong way? The level of general knowledge of most of the challengers is appallingly low. The first three questions with multiple choice are usually not too taxing, yet they get an easy answer right and their teammates applaud like mad as if they'd won the prize money with that answer.
The eggheads are not called that for nothing - they have fantastic general knowlege amongst them all (although one or two are weaker) and if they don't know an answer initially, they can mostly invoke their knowledge to make a more than reasoned guess. A few days ago, Daphne didn't know the answer to two questions in her rounds so to say the eggheads get easier questions is rubbish in my opinion.
Incidentally, how many times when the challengers don't know an answer and it's passed over to the eggheads, do they not know it?