The idea behind Preferred Sites is that you can tell Google which sites you trust most and want to appear more often in your search results. Google will also recommend sites to include in your list based on your search history.
Google’s help page for Preferred Sites explains:
The preferred sites feature lets you set your Google Web Search preferences so that your search results match your unique tastes and needs. Fill in the sites you rely on the most, and results from your preferred sites will show up more often when they’re relevant to your search query.
Alex Chitu of the Google System blog did some experimenting with the new feature and found very interesting results. The most interesting result came after adding IMDb and the New York Times to his Preferred Sites.
After adding IMDB and New York Times, the results for [how to lose friends and alienate people] were changed dramatically: two pages from nytimes.com were promoted to the top 3 results, but they weren’t in the first 30 results for a regular search.
Results from Preferred Sites are marked as such.
Not all users will have the option to participate in the experimental feature right away. Should Google decide to push this change live, it should give you even more ammunition in your case to stop providing ranking reports for clients.
If you were selected to try Preferred Sites, give it a test run and let us know what you think. To enable Preferred Sites, simply login to your Google account and turn it on via the preferences page.