First post in this section for years but thought I would share this one :)
I am playing with some super competitive niches now and have noticed a new penalty on my site and those of my competitors.
What Google has done is basically fill up page one with the authority BBC, CNN, Wikipedia nonsense sites so maybe 2 or 3 commercial sites with enough trust can get to page 1. With these niches you keep on having to build links, of course keeping exact anchor down to a minimum. Then at any given moment you can be in the top spot and be thrown to the top of page 2 and remain there. Whatever you do from then on will not help, it will even hinder your progress.
This is not a coincidence as after the latest authority site update I have seen this on quite a few sites. The only way around this penalty is to 404 the page and start a new one. If you have a source of many backlinks, good for you but if you have to beg your linking partners to change URLS, then it is tough.
The good from this is that instead of penalizing whole sites now, Google does individual pages. A move that is welcomed. The only way to get a site whacked completely now is exact anchor and the dreaded WMT message.