As Marc says, the main problem with the Tiki Wishlist tracker is that the forms are so huge because it loads everybody's usernames. Improved field options within the trackers to allow a list of users from certain groups would greatly improve that.

For the most part, scaling is a non-issue IMO. Who is going to want a list 1,000 long of all tracker items? And who would not expect such a gargantuan list not to take a bit to render? I'll bet if you set the max to 1,000 and get a list of all topics in one of the largest forums, you'll find a similar result.

The vast majority of people who use forums or trackers, or any other feature with a potentially large number of records, have at most a list of 100 on any given screen, so as long as the option is there and restricted to manageable screens worth of data at any given time, scalability isn't going to be much of a factor at all.

It'll probably take less time to pull up a list of 100 trackers in a summary list than it would to actually pull up a full tracker form due to the amount of data in one form from the user list.