We do know that this second international round for Panda included something they called "long-tail" evaluation - for page's that could not be done on the first round because of some iind of capacity limitation.
Tedster, It is interesting that you bring this up - "capacity limitation" and it is scary.
Aren't sites recovering because Google isn't running it again to see the changes they made? If that be the case, it will cause serious damage to larger sites that it is supposed to work against.These sites can only make changes gradually and not all at once.The owners had to go through each page on the site to see if it can be improved.
If google can run this rarely because of capacity limitations, it will take a long time for larger sites to recover.