Position 6 Penalty : When your website come at 1 or 2 Rank on a keyword shift downwards to rank position number 6 in Google search engine. Lots of webmaster saw this penalty in mid of December month.

My Website is effected with Position 6 Penalty ?

Tedster on webmasterworld says

Here are the main signs --

1. Well established site with a long history.
2. Long time good rankings for a big search term - usually #1
3. Other searches that returned the same url at #1 may also be sent to #6, but not all of them
4. Some reports of a #2 result going to #6.

What we can identify so far

A. It's search term specific (usually the biggest and best converting phrase)
B. Therefore, not a url or domain-wide penalty on all terms
C. A little testing on one site seems to show it's not an on-page problem
D. That leaves off-page but on-site, or off-site, or posibly backlink issues

If your website was facing position 6 penalty a lot of keywords then you need to read How I Got My Google Ranking #6 Filter Removed.

Google had a PageRank update with many sites losing lots of greenbars.
I feel there are a lot of more changes still to happen. For some SEO this Google update has been strange and some seo have different expression.

Loren Baker states the Reasons for PageRank decrease as :

Paid Linking : The easy excuse is that they’re targeting paid links, but not all sites which experienced the drop sell or buy links.

Mass Linking : Do we link out to too many sites via Blog Rolls? Does Linkbait just result in TOO MANY links, even if they are natural. Do blog networks use influential linking to their advantage? I think PageRank has been spread too thin and Google is changing its PageRank formula to address the mass publishing which has taken place over the past 2 years.

Devalue PageRank : PageRank is seen by many as the end all value of a web site. Our PageRank dropped but we are receiving more Google search traffic than ever. PageRank does not define site rankings in Google or traffic and it should not be mistaken as so.

Kill the Paid Link Market : If Paid Linking houses use PageRank as a pricing metric, then eliminating or devaluing PageRank will devalue paid linking
BTW, I’d like to add that not all of the links I took off of the Supporters part of my template were paid. They were Supporters, not Sponsored Links.

Barry Schwartz says
Will this impact the selling of links on those sites? Time will tell. Will these sites slap on a nofollow tag? Time will tell. Will this make PageRank less valuable in the eyes of SEOs? Time will tell.

For now, I think Google sent a clear message that they don't want sites to sell links or people to buy links. Will this message stop people from doing that? I don't think so, but like I said just before, time will tell