IIRC, this was one of the things Valve had that Greek economist they hired look into because they were concerned about it happening in their markets. I think the main takeway was that the economies of these games will never get big enough, and Valve was looking at a F2P game with potentially millions of users (for TF2 initially but probably will matter more to their experience with DOTA 2), to have the problem of runaway inflation with values tied to real world currency amounts. And that they only need to tweak the drop rates to prevent it, they didn't have to change the peg or the in-game currency.
I want to say CCG also grappled with this but found it wasn't as big of deal as was potentially feared. That again, only a minor constraint was needed to prevent the supply from exploding out of control.
Of course, they probably didn't model a "fanatical cult fanbase that spends millions of real world dollars" like CIG might need to. (But the experience in real world on no real upper-bounds may be one to look at when considering if it could actually become a problem in the game.)
