Wilburforce - 3:18 pm on Oct 7, 2012 (gmt 0)

Perren - I can't be certain it was Penguin, but the timing of page shifts coincided with Penguin 1 & 2, and yes, penalising on the basis of backlinks makes negative SEO easier (there have been a number of posts in earlier threads on this).

Yet, if the data is good now...that means that they aren't looking at things 'now'.

Not necessarily. Your "slow-releasing lock" would be one mechanism that could account for it. Whatever the case Google have successfully obfuscated the mechanism (and, in my view, any logic that might previously have been apparent in the results).