tedster - 12:12 am on Mar 31, 2011 (gmt 0)
I'm sure that Google continues to "nit pick around" with their algorithms. If last year was roughly 400 tweaks, I wouldn't expect that to stop any time soon.
That's an interesting, if depressing, observation. Please consider adding it to the monthly SERP Changes discussion [webmasterworld.com]. It doesn't sound like pure-panda to me.