I just started a new site less than 2 weeks ago for a 50K keyword and was #4-#5 this whole time. I was getting over 400 unique visitors a day and all the sudden it is gone. I did a AMR blast and some Scrapebox blasts and that was it to the domain. I did create Web 2.0 profiles linking to the domain, social networks, etc. and blasted them with Scrapebox. Not sure what the culprit here is but it sucks. I also had Search Tagging 2 installed and on the sidebar, i had the searches link back to post content. Might play a role, not sure.