I'll be the first one to admit that Apple is anything but open. In fact, they have quite a vice grip over the development of their projects and like to keep things "in the family." But they are rather open toward the consumer, allowing users to add content and now download applications.

Because of this freedom toward the consumer, other cell phone carriers are now "opening up" with what they allow users to download onto their phones. 

However, there is concern that with so  many phone operating systems (Apple, Windows Mobile, Palm, BlackBerry, Linux, Symbian and the upcoming Android), there's bound to be cross-platform woes. Applications developers will have to choose a system, as it may prove too costly to develop for all systems. 

But only time will tell how this affects the app marketplace.

[via NYTimes]