1script - 3:51 pm on May 1, 2010 (gmt 0)
dusky, my answer to your one-question survey is no. I'm not seeing any easily discernible correlation on any of my affected sites. A few people responded to my requests for more data via PM and none have indicated any abnormal Gbot activity. Activity varies, mind you, but nothing on the scale you're describing that borderlines with DoS attack. In fact, Gbot has always (well, last 5-7 years) been able to scale back when they saw performance troubles. Unlike some crawlers of other respected SEs who's name starts with Y. I mean, one bad night of really heavy hits - maybe - but consistently for a week - never seen that.
Speaking of DoS attack, have you double-checked the IPs? On some days I'm seeing 60% of what calls itself a Googlebot coming from IPs that do not reverse-DNS to anything remotely close to Google, Inc.