I recently saw about a 4-5 rank drop (from 3 or 4 to 8 or 9) on a few major keywords we rank for. Never seen these keywords drop like this in the past 5 years, even through Panda. We use a variety of White Hat SEO techniques including outsourcing some link building and the service we've used for the past 6 months with solid results and don't overuse it. I did order another batch of links relating to these keywords lately but nothing out of the ordinary that we haven't done in the past.
I have noticed in the past that sometimes when Google first picks up the links you see a drop for a few days then it comes back up. I hope this is the case. I just decided to post this because the keywords in question I've NEVER seen this happen. They'be been top 5 for the past 5 years and only dancing around 1 or 2 positions max from time to time. Never 4 or 5 like I'm just seeing now.