I just received a chat invite from someone that said Just Cause 2 was available for free for the next 3 days, and provided a link to the Steam website. However, when I went to the JC2 page through the Steam store normally, the special was not advertised. Being of a caustious nature, this makes me suspicious; it could very well be a trap to get people to login to the site and steal their passwords and subsequently their accounts. If you choose to take the offer, please be careful and change your password immediately after.