chrism - 8:13 am on May 25, 2010 (gmt 0)
Overnight our long tail keywords have returned, the ones i monitor have returned within a position or two (always lower) of their original position logged out, but in their old positions logged into personalised search.
Interestingly, i am now getting traffic to more pages overall, but no noticable increase in traffic compared to just prior to the drop off (which for me happened on April 9th, and bottomed out April 15th). I assume this means we're getting traffic to more pages, but due to slightly lower rankings the overall traffic is similar. I dont know if anyone else has seen this but we also got a brief return of traffic on may 15/16th.
We also had the patch of huge googlebot activity over the last couple of weeks, although i havent noticed the deluge of spam sites rising to the top that others mention.