Thanks for the link, really interesting piece.

Both wikipedia and NPR are also lucky because the people who see their value are the same people who have money to donate. Facebook and Twitter aren't so lucky.

You don't think enough people who get utility out of Facebook and Twitter have money to donate? I don't have any numbers to argue with, but I'm not convinced that this is obviously the case. I would think that if Facebook put up something saying "Hey, we're getting rid of ads and trying to build a community-supported platform," some of their 1.2 billion users would be willing to put some money in.

If you start giving people who pay a bunch of features, those who don't pay will be left out. If they are left out, you can never turn them into paying customers.

Doesn't the freemium model completely contradict this assertion? Reddit Gold gives additional features to users who pay for it, and those without Reddit Gold don't seem to be complaining.

Without profits, those people can't put 100% of their time and energy into the product or service.

Are you sure you're not mixing up revenue and profits? I'm not an expert in accounting, but I'm pretty sure a company can still operate at full capacity if it receives enough money to pay its employees' salaries and other expenses. Or perhaps you mean "profit" in the more general sense of "making a boatload of money," implying that the amount of money to be made from donations or premium features is not enough to sustain a useful platform. That's a legitimate concern.