As always, I'm typing through ideas so forgive me if I say what you already know.
We're trading social currency, and under that currency Hubski has created a transactional basis that can afford you. They clean the social sweat equity of a mass into something intellectually compelling enough to engage you.
By creating a direct conversion to financial currency they are taking a known value in your life, the value of your time, applying it to the previously non-financial social currency and the exchange rate is far lacking. This is the Ariely argument and, as he predicts, it elicits insulting feelings.
I think where your value add system, and the value add system I've proposed before, gets it wrong is in who we are providing value for. The common focus of value add systems here, and everywhere they are applied, is that the value add should be to the consumers. I'm sure this is ultimately true, but the Ariely argument makes the necessary conversion financially impractical.
There is, however, a very large industry that works on a value add model that does not focus on adding value to the consumer. In fact, in many cases, it removes value. An ad agency gives money to a community's leaders in exchange for time with their audience. Because they have no social currency, their message is promised a spot that is more difficult to ignore. This is where donation based services like NPR and PBS make up for their lacking revenue, which shows there's money to be made in value adds that don't target the consumer.
But, as we are all aware, providing value adds to advertisers takes away value from the community. It's digested as a necessary evil because no other alternative is immediately available. You could try to only advertise products valuable to the community, but those products would do well without financial capital as they have an excess of social. You could allow individuals to buy space on the site but the only people who would do that would be those lacking in social capital. In fact, it seems, the only people who would need to spend on financial capital would be those without social capital and would, by that very contradiction, be a pock on the community.
But what if you could create a value add system for members of the community that weren't the consumers, but the creators. Reddit tried this with the marketplace and subreddit ads, neither of which was enough of a success to make them self sufficient, though whether that's a flaw in the system or the late implementation of the idea is debatable. But I'm thinking more of the creators of the site itself. Is there such a system that my contribution could create tangible value to the site creators, the other side of the Community, which ultimately creates value for me on the consumer side.
Of course the simple answer is direct donations, but that just feels so boring. Not to mention, as a system it's not very self sustaining and you constantly have to slog to keep donations at proper levels. There must be some other system, some self sufficient way to marry social and financial capital to the benefit of the community.
If you've reached this point and you're looking for some conclusion or answer, I'm afraid you won't find it. This ramble was purely to purge some ideas. If it gave you ideas I'd love to hear them.