... there was a network scale attack I pointed out to Gavin and the other devs after observing namecoin network getting "hung" for months by miners joining and leaving en-masse due to mining incentives and price fluctuations ...

if a well-resourced 'dishonest miner' attacker could build up a significant of quantity of mining power and ramp up hash-rate by bringing on-line an ever-increasing amount of compute, selling all btc the whole way and simultaneously drive price lower over the same period, squeezing out 'honest' miners ... then in a final act take all their mining power off-line during a final dump of price then it would leave the network hanging at very low block solving rate (long confirms) waiting forever for the next retargetting and a low price and take a toll on confidence ... the fix was to allow for a 'special' retargetting on the downside if it hasn't happened after a time-out, not just the set 2016 blocks.