Wikipedia is hard to monetize, but it's still a "big thing." Luckily, it's organised in a way that doesn't require S&P 500 revenue targets.
The economics of startups->dragons is such that it's near impossible for certain mass-market services exist even thought they are useful and economically viable.
The internet makes it possible to serve tens of millions on a modest budget. In theory, this enables a business to exist on a modest budget. In practice, serving tens of millions represents more-than-modest potential and that chance, even if quite small, is worth more than the business.
Say a service like meetup makes $20m revenue, expenses of $16m and is growing @ 10% pa. In theory, a nice business. Should be worth $50m-100m.
In reality though, a business like this is not just a business. It's a chance, however small, to be the next FB. At the least, it's a chance to be a FB acquisition. Even a minor threat to FB could easily be worth $1bn.
Chances of success don't have to be very high for the "risk the house" strategy to dominate. A 10% chance @ $10bn is worth $1bn. Systemically, that means a meetup is destined to be continuously bought or funded by investors taking that chance. It can never settle into a steady, viable state where it just does its job.