Say I'm into motorcycles, and I am a regular at motorcycle-forums.com where I dispense helpful advice on everything from tire pressure to tappets. Over time I deservedly acquire a reputation as That Helpful Guy, and the grateful votes of other users accumulate. One day I decide I want a new bike, and head over to the marketplace subforum to purchase one. Turns out that Alica has just the bike I want! Naturally I want to use my accrued Biker Points to get a discount.
Now, in a closed economy. Alice might be delighted to have my BP - she could trade them for other goods and services with other bikers, and there might even be a social value in having dealt with me (a good few specialist websites maintain informal 'trusted buyer/seller' lists which saves members money vs. low-trust high-fee markets like eBay). But what if Alice is done with biking and just wants to get rid of her Vroomatic 5000 so she can take up windsurfing or something? My BP will be of little use to her on the ocean wave, and there may not be enough transitional activity between the Biker and surfer communitites to establish a maingful rate of exchange, so instead you end up with a bunch of shady pseudocurrencies, sort of like penny stocks.
One way I can see it working is if quality websites charge a small joining or membership fee and a portion of that constitutes an initial pool of points. Alternatively, a portion of ad revenue might be convertible into points, as those members who consistently make valuable and informative contributions are a key part of the site's draw, so it makes sense for the operator to subsidize the most 'productive' members.
I may have got completely the wrong end of the stick here, and you only meant to substitute reputation for cryptographic proof-of-work, but I'm guessing form your slides about inequality and different concepts of value that you're looking to examine the notion of wealth in more subjective contexts, rather than just authentication.