Actually, yes. Every con has a max attendance allowed, generally in the hotel space at a time, due to fire-code.
A couple of years back, Kumori actually had to put a cap on the attendance in the line. They had staff running like mad up and down the at-con-registration line counting people and double counting people and making announcements that a cap was in place and if you're after a certain person in line, it was pretty close to a guarantee you wouldn't be able to purchase a badge.
Right now, our largest issue is fire-code capacity. That's why lines for large (or in-demand) events are stuck outside of the building. This has no bearing on whether you can buy the badge or not, but it will affect if you can get in or not. That's also why certain events have the "tickets" to attend (you need both a badge and a ticket to attend those events).
