mediapartners-google bot activity spike today

anyone else feeling this?

[linear]

Right now I have 10 instances of Mediapartners-Google bot on my site. This is notable becuase:
a) that's a large amount for my site
b) the user agent string has been changing recently, and is currently

Mediapartners-Google/2.1 (+http://www.googlebot.com/bot.html)

where a couple days back it didn't contain the URL.

It's crawling normal static site pages, not forum pages or anything that would typically be associated with high activity. I can't se that it's caused by a spike in normal readers either. Anyone else?

[dataguy]

I was pounded by the mediapartners-googlebot for about 24 hours, ending last night. Seemed that they were frantically trying to re-crawl as much as they could. I wonder if there was some corruption in their targeting data, or maybe just some improvements that required a re-crawl.

My problem is that they were crawling so hard that my database servers couldn't always handle the load, so for some of the pages, all they received were error messages.... It was only a small percentage of the pages, but the bot rung up over a thousand errors yesterday....