This line of argument raises two interesting issues. First, consumers are willing to pay for "bundles" of content as long as their collective quality is vetted by an intermediary. We still buy newspapers, subscribe to magazines, and pay for cable television. Maybe this is because the cognitive costs of assessing the quality of millions of slices of content are too high, and we'd rather let someone trusted do a first screening.
More interestingly, we've been promised a micropayment system for over a decade now, but nobody seems to have succeeded in creating one with widespread adoption. Instead, we have trusted intermediaries like iTunes who use a standard payment system (your credit card) to "microcharge" you for 99c songs and $1.99 iPhone apps. This seems to be working out rather well for Apple, who generated a couple of billion dollars worth of transactions in 2008.
Perhaps this is the future of micropayments for content -- combining trust in payments with trust in taste or filtering. If we have enough faith in the intermediary, we'll let them narrow our content for us, and trust them to charge us right. Its also loosely consistent with why eBay owns PayPal. At first glance, this seems less appealing and efficient than a stand-alone micropayment system combined with technology-based filtering and an open market for content creators. But if you factor in cognitive costs and a growing body of evidence that consumers do pay more for online reputation, placing your "taste" and transaction risk in the hands of the same trusted intermediary might not be all that inefficient.
That still doesn't solve the micropayment mystery. Why hasn't a good micropayment system emerged? The technology exists, there's lots of money to be made from being the standard, and there's certainly plenty of microcommerce languishing in its absence. There's got to be something about what consumers value in a payment system that is missing from all the efforts we've seen so far...