My friend's 6 month old site saw a traffic dip around 20th March when Google Announced penalizing over optimized sites.
The very next day I got a call from him saying that he did nothing to trigger over optimization penalty. He wanted me to have a look into his site's Analytics and Webmaster tools to see if I can come up with a reason for such a hit in traffic from recent Google update.
Why the Drop?
After digging Google Analytics and Google's Webmaster tools I realized that he has done a very common thing that many of us do that could be the only reason to trigger such a fall. He has few sites in the same niche and all he did was place a site-wide link to the new site from all those established sites.
I was very keen on knowing the exact cause of such impact because the question that I had in my mind was - Can a site-wide link impact the penalty of over optimization. As far as my understanding of over optimization goes the site and blogs for giving backlinks were penalized and de-indexed (I updated my Link Building Strategy to avoid such Blog network).
In fact I also link to my sites site-wide from related sites. As an example IMTips is linked from my MBA Forum site-wide in the top yellow bar but there is no major impact on IMTips for over optimization.
The Real Reason
After discussing the links details I realized that he had a do-follow site-wide link and IMTips incoming site-wide link are all no-follow. It could be the only reason that his site is penalized but IMTips is not penalized. Apart from that site-wide links means there is no variation in anchor text link and March Google updates were more focused on Anchor Text enhancement.
Now we probably know the real cause of fall in his traffic.
So what's next?
I asked him to remove links from those sites or at least make them no-follow i.e. links for traffic and not for search engine benefits and after 3 week's his feedback is his traffic is recovering from Google but very very slowly.
Share your March traffic impact from Google in comments below.