Typically when a tournament overbooks (as they used to regularly at the Wynn and now do occasionally at the Venetian) they hand out alternate cards and the alternates wait until a seat opens up.

If a tournament claims to be open until a particular time then getting into the money can't be determined until the registration period is over because the number of players in the money is based on a % of the total registered.

You can know that you have dipped below the 12% or 10% of the total registered players and that everyone who is currently playing would be in the money if the registration period was over. But it would reward players who have very few chips and make playing hand for hand on the bubble virtually impossible to perform. This would in and of itself make it likely that one or more players would stall prior to the fungible bubble.

For these reasons I would keep the registration open until the scheduled time. But if I was the cardroom there is another reason to do it.

There would be massive registering for the tournament just before registration ends if the all of players already playing were "in the money". In fact you could be fairly assured that there would be quite a few players more than the bubble after registration ends.

And of course there is the issue of a guarantee. If there is one then the cardroom wouldn't ever plan on shutting down registration before the given time.

A few years ago at the Venetian I was playing in a guaranteed event. I think the guarantee was like $600,000 (it could have been $400,000). About an hour before registration ended they were short by over $100,000. And I felt like it was a sure thing that the tourney wasn't going to make the guarantee. And yet. They crushed the guarantee. Apparently there is quite a network in Vegas that contacts players when a guarantee looks like it won't be met.

This is all true (and I enjoyed the Venetian story) but I'm not getting the solution you're proposing. So you launch a tournament at noon with 100 players, 10% get paid, late reg until 2pm. By 1:45 you have 200 entries, 21 left, and a player busts out on the bubble at 21st.

So you keep taking entries, right? Aren't they buying almost into the money?

Yes they are buying into the money but it won't last long. Other people will continue to buy into the money as well until it is no longer buying into the money.

But a bigger problem is when they are on the bubble do you play hand for hand? And then what happens if another player enters or five more enter. You stop playing hand for hand?

I would say that you can't know if you are in the money until the registration period ends. Then if everyone is in the money so be it. But I doubt that would happen...