Shirky vs. McCloud
Scott McCloud and Clay Shirky both make convincing, solid arguments, and I don't think that either of them are wrong. I think they are discussing slightly different aspects of the same issue, and that's why I think they're disagreeing.
When Shirky says that if you have to pay for something and you can get it elsewhere for free, I am not sure if that it refers to something of the same category, of to the specific thing. McCloud seems to think it is the former, in which case he makes a good point that users won't be satisfied with the free items (Donnie Darko vs Dances with Wolves). In reality however, you can probably get the actual thing for free anyway, so then obviously no one would prefer micropayments. I think Clay is assuming that you can find high quality content for free (legally), whereas McCloud isn't really agreeing with this assumption.
I think that Clay is right in that having to pay, even if the amount is microscopic, is a significant barrier to deciding to acquire something through buying it. I think that both of them should take more seriously into account the reality of the situation (McCloud mentions it briefly in the end) that if users can find the exact same thing for free, with the same ease, they will probably get the free version.
I think the one succesful example of micropayments is the itunes music store. I believe it works well because it manages to automate the process so much that you do not feel the "mental transaction costs" of paying. Having itunes on on your computer, you are usually signed in, and it has your credit card info, so whenever you want something you can just click and click to confirm that you want to buy it (i think, to authorize the transaction) and you're done. Very painless, and it doesn't feel like you are spending that much. Interestingly, this example is sort of mentioned by McCloud, who mentions mac users buying many many songs online.
I think users want to take the path of least resistance, and paying (any amount) should defintely be calculated as an instance of resistance. If you can get the exact same thing just as easily, for free, then people will choose that option.
