How are you thinking of designing the app, Peter?
There are certainly plenty of blogging, audio, video sites that do similar things. YouTube's become a titan letting you post your own videos. Odeo let's you do exactly the kind of audio recording over internet that he's talking about. What requires the user to have the framework installed? I admit, I'm not terribly familiar with multimedia apps, but I don't understand why ASP.NET would be uniquely unqualified to build one.
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