A requester apologizes

Sometime in October, a number of very experienced Turkers started getting blocks out of nowhere.  Some of them found their accounts suddenly closed.  They had no idea why.  Here's why:

We want to let everyone know that we are extremely sorry about the mass blocking - we did not realize that blocking you had permanent effects on your records as workers, and we are very sorry if we caused problems to your account.

We have unblocked everybody, and we have contacted Amazon asking that the blocking incident be removed from your records. We will do everything we can to make sure this is done and that your accounts will not be in danger due to our blocking.

We will never use blocks in the future, and again only did so now because we did not realize the negative effects. Please let us know if there is anything else we can do...  link

This kind of thing happens all the time on Mechanical Turk.  Sometimes the problem is figured out.  Sometimes the requester fixes it.  Sometimes they don't.  When things fall through the crack, it land on Turkers, and it's not money that lands on their heads.