It's looking to me that the Wikipedia business model is the correct one for a community site like Reddit. What are the chances of a Reddit clone surviving on donations?
I'm not sure what you mean here; are you referring to the annual donation drive? I love this model, but I know a lot of Wikipedia users who absolutoly hate the (admittedly non-invasive and pretty respectful) banners requesting donations.
They are not lying when they say "if everyone gave $5 the appeal would be over today". It's much easier for them than for a local PBS affiliate because of the huge user base. As the internet grows up, I hope users will learn to value things appropriately and not expect them for free.