Since they were released, many people complained that the new 2011, 2012 MacBook Pros had graphics problems. The complaints ranged from not connecting to external monitors, flickering, and and the worst, annoying white lines afflicting the screen much like this.
Affected computers include 15- and 17- inch MacBook Pros from early and late 2011 and both 15-inch Retina MacBook Pro models. Apple's page provides a tool you can use to check your system's eligibility. Symptoms of affected computers include "distorted or scrambled video on the computer screen," "no video on the computer screen (or external display) even though the computer is on," and unexpected restarts.