For years the traffic metaphor was a bad but widely used one to describe the visitors viewing your site. A few days ago the new Tesla Model S has been unveiled. Most people focused on the environmental impact of this visionary electric car but some noted that the Google founders are big investors in Tesla Motors.
One of the first mass produced electric cars might become the first Google car as well. The metaphor of traffic will become reality. People will drive around like they browse and Google will offer local search results and ads on the go. 
