I can't believe nobody has responded to this with [citation needed] yet! ;)
OK seriously now, I kind of remember some rumbling about the challenges facing the project: crowd-sourcing a general purpose encyclopedia, generating enough money to keep things running without showing ads - who would write the content, the quality would be terrible, etc.
I'm not sure it was "widely" considered as doomed, but I'm also sure the breadth and depth of topics and overall result ranges from outright shock to pleasant surprise of the naysayers.
Wikipedia has flaws but overall it is a great reference on a massive variety of topics. Here's an anecdotal example: I'm a hiker and a friend and I ran across a weird looking fruit on the trail. After taking pics and asking around we were told it was an "Osage orange". Never heard of it, so I went to Wikipedia and found a lot of info and yes, that was definitely it. I can't imagine Encyclopedia Brittanica, World Book, any of those I remember from my youth, would have had as much info on the Osage orange!