One further thought, starting from Wikipedia as an obvious example. In some areas, it's very good, in others bad; the bad bits could be brought up to a decent standard. But the crowd-sourcing model will never get one thing: the coherent, consistent approach and style you get from an editor.
Two things in particular:
1. Consistency of approach and level. Some Wikipedia articles, in areas I know about, are excellent. Others reprint the 1911 Encyclopedia Britannica. But in anything mathematical, they are useless to me, because the introduction gives a verbal description of the formal kind you'd get in a textbook, and then it's straight into deriving the equations. Technically it may be very good, but useless for someone innumerate, but trying to grasp what can be grasped of the ideas in a general way. An editor would ensure that all articles have at least a reference to what can be said to the ignorant seeking clues, as well as technical discussions.
2. Point of view. Crowd-sourcing tends to either a neutral pov which stops a lot of things being really discussed, or produces really quirky or extreme irrelevances (I think of a site I've seen a couple of times: an invaluable resource on German motorcycles, but consumed with hatred for the Brits).
What would make an internet publication stand out is a consistent tone, and a reasoned set of opinions/judgements (though not too intrusive), and this could be done by rather a small team responsible for putting the thing together. Hard to make much money on the net, but perhaps not too much money is needed, as it would only have to support the full-time editorial team: as people say, nobody has expected to make a living writing for special interest mags.
And perhaps it would be possible to try parallel print and online publication, as a way of testing the water. I can remember when I spent a lot of time in magazine sections of big newsagents (good grief, that seems a long time ago), but to be honest I wouldn't seek out a print copy of Aeroplane now: but I might quite well risk an online subscription.