The indie developers involved in the potato sack sale say that they were given "free reign" to design the ARG, as well as "access to any IP we wanted."  Edge have been catching up with the potato sack developers to find out exactly how the enormous ARG came together. 

Audiosurf creator Dylan Fitterer explains how Valve initiated the ARG. “ Valve invited a bunch of us indie developers to come out last December for a 'Cross Game Design Event.  It was a bit mysterious, but definitely sounded like fun." 

“Jeep [Barnett, Portal 2 programmer] coordinated with us most closely, but Gabe kicked it all off.  He asked us to work with them in creating an event that put launching Portal 2 into the community's hands.  We were given free rein to design it and were also given access to any IP we wanted.” 

Dejobaan president Ichiro Lambe “It felt very natural.  Valve gave us a framework and said: 'You know all about GLaDOS.  Now, she wants us to break out into the world.  Go make it happen.'" 

Fitterer explains that the number of people playing Audiosurf during the ARG jumped from 300 a day to 6000 a day.  There's no news yet on the number of potato sack games sold during the ARG.  Edge's full featureon the ARG is set to arrive tomorrow.