Speaking with allthingsd.com, Nintendo President Satoru Iwata stated that when it comes to the freemium model that many free-to-play social, MMO and mobile games enjoy, "Nintendo is not interested." Clarifying the point, Iwata stated that Nintendo is not interested in giving away software for free; feeling that it would affect the quality of the product and that Nintendo is not interested in cashing in on the quick earning free-to-play market at the expense of the gaming market's perception of what Nintendo offers.
If we are going to destroy the value of the game software once we have done so, its a difficult job to recover from that situation.
Iwata yielded the point that some of these models do tend to generate a substantial amount of revenue through microtransactions and advertisement, but he's not sold on the idea that the free-to-play craze is going to last. While maintaining that Nintendo is not interested in the model, Iwata does state that if Nintendo were to do something similar, it would be something completely different.
Source: All Things D