I just logged in to one of my old blogger blog and noticed that the daily traffic has decreased from 2000 u.v. to 300 u.v. Take a look at the screenshot of webmaster tools: The sharp decrease in traffic started on 18 December 2013... Was there an update on 18 December??? I was never involved in any sort of link building as I was targeting local keywords and there was not any competition at all. So it not any neg seo... I have no idea how this happened.