What whatever you want to call it it's some penality or filter that doesnt allow it to rank on the keyterms anymore it seems. For example I ranked on the first page for popcorn movies, now its on page 62 or thereabouts. Were not talking about de indexing just a sandbox or penalty due to link velocity imo.
Here look at the graph from Google:
The odd thing is I see another site with a worse link graph than mine: meaning that most of his links are blog spam, whereas mine are varied, pretty much same age of site. Yet something tumbled me over a cliff.
One thing to keep in mind when looking at a sites links is that you are not seeing all of them. Google shows you next to none and while Yahoo shows more of them and can give you a good indication of how many links a site has in General, the links you see in Yahoo do not really mean anything at all when it comes to ranking in Google. One site I am working on now has over 6k Google indexed links as of last weekend and shows 3300 in Yahoo and 26 in Google.
Why does it have to be a penalty? Just because you do not rank well enough to get on the first page does not mean that Google is somehow singling out your site for something you did?
There is a huge difference between being punished for breaking the rules and not doing well on a test. It most likely means that your site profile is just not good enough to rank well according to the same algorithm that everyone else is using (
ie: not doing well on a test).
You need to test different link building methods and see what works and what does not work. Take what does work and replicate and add to it so you can do better on your next site.
There are a lot of questions you have to answer when comparing your site to other sites and some of the information is hard to come by for the other sites.
How old is your site?
How many links do you have and how old are they?
How many high PR links do you have?
What has been the pattern of your link building?
How many similar or supporting keywords does your site target?
All of these things are giong to make a difference, you can not just compare the number of links and say "hey I have more links than him I should rank higher" It does not work that way.
For example I have seen some very strong evidence over the last year that Google gives more weight to links as they age. This means that the link you got yesterday will be worth more in Google's eyes six months from now. This gives two advantages to older sites, the actual age of the domain and the fact that they probably have a lot of older links. If you think about it, older links should be worth more. A long term stable 3 year old link is a much stronger vote for your site than some link that is deleted after a couple of weeks just to be replaced by another one.
Seriously there is no spoon.