affiliation - 8:57 am on Oct 3, 2011 (gmt 0)
What I have noticed, is linking may be ane of the demotion factors, in one set of results I watch the #1 has gone, linking was a factor in the site being there. In one of my own sites, I have been trying the link game, also have been demoted.
Another demotion was a site that I had included in Twitter, minimal followers, so what I would take out of that is if you put a social aspect to your site and get little followers, G perhaps think site is not popular.
The same for +1 etc, not enough +1's and your site in G's eyes may be unpopular. Best bet is not to go down the +1 or social route, at least it's not letting G see how popular or unpopular you are
The sites I have that maintained or improved their positions are sites that I have did none of the above, but sites that I have delved in the above have all been demoted.