If it turns out to be a viable revenue stream, we might see more free games released in hopes of attracting the largest user base possible, which would in turn make the game's ad space more valuable.
Another possible upside is that developers could use the money to make better games, provide more frequent updates, or maybe even spend it on live content.
Although it's difficult to predict at this stage how annoying ads in games will become, the greatest concern that gamers have is that the ads will be out of context. A current or near-future urban setting without billboards is inconceivable, so many games already have billboards in them sporting fictional products. The use of real products in such cases may even make the setting look more legitimate. Nevertheless, it would take a lot more imagination to integrate Coke or Chevy ads gracefully into medieval fantasy environments.It's entirely understandable that gamers are wary of these developments. After all, we've seen advertising invade various other forms of media with some unpleasant results, to say the least. While we tolerate TV ads with our thumb on the mute button, they've run amok on the Web if you dare surf without a pop-up blocker. Spam has nearly crippled email, and voice mail could be doomed to the same fate. I'm already having visions of Ford logos in loot windows and NPCs hawking mutual funds.
Nor is it certain that the revenue generated from ads will be passed on to the consumer in any way. In some cases it may be put into offsetting rising development costs, in other cases it may be used simply to increase profits.

