While the GE AR campaign is probably the most successful viral campaign so far, I think the upcoming Doritos AR campaign with the rock/punk band Blink 182 has the potential to surpass.
A special symbol on a limited edition bag will be used as a marker for the concert that will be played in your room using Augmented Reality. There will be some feedback after the concert in the form of audio pickup, and if there is enough noise (I can guarantee there will be), they will come out for an encore.
The bands breakup in 2005 and reformation in 2009 will probably guarantee a large audience for this AR stunt. I suspect it will be a successful one that will launch their summer tour.