They don't try to be some post modern pseudo-socialist dream of everyone contributing. Not everyone SHOULD contribute. Not everyone knows enough to make a valid contribution. Not everyone actually knows the facts, they just think they do.

The ability for anyone to change anything is wrong - people use it to mess around - making up entire biographies for people that are entirely false, saying they're dead, just to try and be funny. There needs to be responsibility, accountability and, frankly, dictatorship from above on who can and can not contribute or at least vet any and all contributions before they go live.