Does Google give preferential treatment to advertisers?

From day one, Google proudly claimed that they wanted to "level the playing field" allowing the little guys to compete with large companies on the web. This was a tradition, and for a long time Google ranked sites based on their own merit and not on the size of the marketing punch behind the site. The idea was to create a more democratic internet, and Google was applauded for it.

I think that Google has strayed from this major tenet of their mission, and I have at least minimal proof that money has the power to change Google's mind about a website.

I've found 4 sites that took huge hits in the SERPs for their major keywords. I'm posting what the webmasters of these sites have experienced, but I won't be naming their sites or the keywords involved because of the fear of the Google wrath.

Site 1
The first site was completely banned from the index, even though it was an established site with over 5 years of high rankings and a good level of trust from Google.. They used an SEO firm that utilized some black hat techniques and Google caught on quickly. The black hat techniques were fixed, and the website met all of Google's guidelines. They requested re-inclusion, but their site still wasn't indexed after 2 months of waiting. Again they requested re-inclusion, and waited 30 days. Again, they were not indexed. 90 days after the ban, they started an Adwords campaign in an attempt to get traffic back to their site. About two weeks after starting the Adwords campaign, the site was re-indexed and started climbing the SERPs for their main keywords. It's hard to tell if one of the re-inclusion attempts was finally serviced or if the Adwords campaign had something to do with it.

Sites 2 and 3
Two sites were not banned, but had precipitous SERP drops for all their keywords. Both were owned by the same webmaster, and the two sites linked extensively. Both had good track records of white hat techniques, so the SERP drop was completely unexpected. The owner attempted to contact Google, to no avail. The sites were still indexed, they just didn't rank in the top 1000 for any of their keywords. All pages on both sites remained in Google's index, but they couldn't be found without using the site: operator. Both sites also ranked below 1000 on searches for their domain name, a search that should have them at #1. Once the owner put Adsense on one of the sites, it jumped back up to its normal rankings for all the keywords. The other site kept the penalty, until he put Adsense Ads on it. Both sites were able to regain their original rankings after putting Adsense on the sites.

Site 4
For no apparent reason, the fourth site got dropped from the SERPs for all the major keywords. Unlike sites 2 and 3, however, this site had some top 50 SERPs and some that dropped into the 900's. For three months, the site languished in poor SERP positions, and the site dropped from over 1,000 indexed pages to about 50. However, once the owner purchased Google advertising, the site immediately starting ranking again for the keywords. The pages are slowly getting re-indexed, but this was a major blow to a website that received most of its traffic from Google.

My Thoughts
I've actually spoken with many more webmasters who have had the same issue. I used these four examples because the site owner was upfront about what was going on with their site and gave me inside information and let me analyze their sites myself. So it's not a single website that coincidentally had this happen to it.

My understanding was that the entire logical and physical infrastructure for the Adwords/Adsense and search technologies were separate and disparate entities. If they are not, and rankings are being inflated because of advertising dollars is incredibly disturbing. Not only does it kill my opinion of Google as a progressive company, but it lowers my trust in Google's rankings.

I don't think its a coincidence that the rankings changed after becoming a part of Google's money machine, whether through Adwords or Adsense. Those are the two parts of Google that bring in the most money, and to have them compromise the natural, organic search results brings money into the equation. Is Google really "for the little guy" anymore?