The ACP has established quotas by country for PBP 2011. They have published information here.
Some analysis of how the quotas will affect the US contingent can be found on the RUSA site here.
The effect of pre-registrations on the quotas can be viewed on the PBP site here.
Updates on quota utilization will be updated here.
A couple of notes:
When a rider receives, for example, a "dossier number" of US-258, it means that he's the 258th PBP rider to register, not the 258th US PBP rider to register. In the case of #258, he's actually only the 72nd US rider to register. So our quota is not filling up as fast as it might appear to be.
The filled quota represents the riders whose preregistrations have been validated by their country organizations. I've been keeping up pretty well with validations for our riders. Other countries may be moving more slowly, especially those applying some separate quota criteria (I know that Australia, for example, has a separate regime rewarding total distance ridden last year).
The US quota will not fill at the 1000/1200 nor the 600 stage. By then, we should have a bit better sense of how many of our preregistration-eligible riders are actually preregistering
It's theoretically possible for our 1200/1000/600 riders to fill our quota. But it won't happen. We'd need near 100% participation from that population (719 of about 740).
Folks who can wait until late June to make plans should be aware of important dates in June. Any space for a pre-registered rider who doesn't complete final registration will be released on June 20th and more spaces will likely become available within our quota. So if our quota is filled after the 300k preregistration, for example, riders who did a 200k last year should still preregister at the appointed time, to get their names on the waiting list. Similarly riders who didn't complete any ACP events last year should register on June 11 to get on the waiting list. On June 20th, riders will presumably be accepted off the waiting list when spaces are freed up.