well developers her will tend to make apps which suit their own needs, or an app which will help many others, if you want an app that will suit your need but help zero or few other people, then either code it yourself or else offer to pay for it. as for frostwire, it sucks, big time, there are much better ways to share files, already available on n900. there are already apps for social networking and for communication, and n900 will handle facebook etc almost as well as the pc will, so theres really no need for an app.
before you go asking for appps think how much time and effort developers need to put in to make it, and usually do so for free.