Source: http://gizmodo.com/5932994/google-search-results-can-pull-from-your-gmail-now
Your email is basically a huge repository for information that you need. That's where you store travel itineraries, party details, package tracking numbers, phone numbers, and countless other important bits of data. If you enable the trial, Google will pull relevant information from your emails and display it alongside your search results. Researching an upcoming trip, for example? Your airline confirmation email will pop up in a right-hand pane.
With the launch of Knowledge Graph earlier this year, Google's whole approach to search changed. Folding Gmail into search results fits right in with the new mantra. Before, Google wanted to provide you links to information. Now it wants to scrape the sources and provide you with the information itself.
It's a further uniting of your Google identity, which could be seen as a further depletion of your privacy. But Google heading this direction is inevitable, so the best we can all do is maybe sit back and enjoy the benefits while doing our best to forget the creepy negatives.
The trial is limited to users with @gmail.com email addresses, and it will only be available on Google.com in English. If you sign up and you don't like it, you can later opt-out of the trial. No word on when a wider roll out might show up. [Google via The Next Web]