I noticed this a while ago, think it was on theregister website, I dont think much to it, first of all it would be unusuable on Krapcom's Krapoo and second it isnt any good if your internet goes down, not forgetting that you no longer have any tangible goods...
Remember what happened to Halo 2 earlier this year. you can still play campaign but even that would be impossible on a service like this

, should your favorite game be discontinued..