It seems that we weren't so behind in South America vs. the US in matters of cell phone openness. It seems that in the US carrier also had a closed garden infrastructure like in other parts of the worlds fending off would-be startup to use their network to create new products to post content online.
A recent news has shown that at least this is changing an several 2 startups Q121 and Rabble are already taking advantage of this new scenario to create a better improve social networks using mobile phones. In an interesting analogy (similar to a previous link of mine) the article goes on saying that 'This "walled garden" concept harkens back to the closed dial-up computer networks of yesteryear, such as AOL, Compuserve, and Prodigy'
This is a great step forward for the mobile phone to become the next computing platform.