I could see 100 people coming, the thing is, a majority of those probably won't be major prospects.
Right, I could see it happening. Between those expected and those considering, all you would have to do is triple the list and you'd be approaching 100. I don't think that's unrealistic and like you said many won't be elite prospects garnering national attention.
I would have just rather heard that figure from someone else first---Rivals, ESPN, another newspaper and so forth.
I've heard the new staff is in favor of one big JR day to make a splash, as opposed to several smaller ones.
Theories:
1) It gets more publicity if it's a once a year event.
2) You can compare everyone side-by-side in one day instead of trying to contrast/compare guys who visited separately.
3) Convenience. You get it done quickly and you don't have to worry about planning/organizing multiple events.
4) With it only occuring once, there is more pressure on prospects to come, because the window is small. Getting everyone in one session also allows people to make friends and influence one another.