Yes, there is a maximum number of ballot lines, and I know last year (2008) we were right up against it. Mitch did some tweaking of his program in between, and opened up more possibility. We had some leftover space this year (2009), but as I mentioned, with new coasters coming every year, something's got to give.
Yes, I would expect the mega-lites to get a grouping sooner or later.
Mitch has set the minimum for inclusion at 2% of the # of ballots recieved. It used to be a fixed number, (I believe it was only 5 or 6 until 2007) but he liked my suggestion that the number should be flexible with the growing number of ballots being recieved. This year, that magic number was 13 riders for the steel ballot. Between 10 and 13 riders, was 'the grey area' and those coasters got an asterix (*) in place of a rank number.