THQ launched a promotion today for their Metro Facebook page. Anyone who likes THQ's Metro page will receive a free copy of Metro 2033.
This is a smart promotion to get people interested in playing Metro 2033 before the sequel Metro: Last Light releases in March 2013, not unlike how Borderlands was given out on PlayStation Plus before the release of Borderlands 2. By using Facebook, it will also inform interested users any updates on the Metro: Last Light, making it an invaluable marketing tool.
Source: Facebook.com
