As in the PC operating system market, share means software and software means users making the market share grow.
In such a contest appears clear that the key for having more and more users is to give the possibility to have more and more software. Google is trying to create a community around its android in order to give innovative service to users, but it can not be enough. Apple after the first prohibitionist phase released iPhone SDK, but it is too limited and their phone is still a fashion object.
Why I should abandon my S60 Symbian? I don't think I could find more features, I don't mind of having a cool but useless iPhone and Android is still more a prototype than a product.