I think Google will change the search algorithm within a few years. A lot of content on the first search results pages of Google isn't there because it's high quality it's there because the sites have a high PR because of many bought or auto (blog) generated backlinks. Google engineers know this but it's hard to fight and determine what's real and what's not.
My guess is the SE results will be more based on your previous searches and time spent on websites with adwords or double click ads, and it doesn't matter if you're logged in or not. They just use a cookie and/or IP and some other methods to determine who you might be.
Google is already doing this with there "personalized predictions". It will only get bigger.
What this means for webmasters is that they must focus again more on original content and other ways to attract visitors. It will make the business of buying and selling text/web links useless.