I would say when Facebook arrived. But it wasn't so much "shift to corporate-owned", it was more that it allowed non-techies to put stuff on the internet for the first time. Us techies, we already had our hand-coded html web pages hosted at some (probably commercial) provider.

I think the answer is "usability". Look at all the community-made, non-commercial projects. They tend to suck because they weren't built for you. They were built for people with similar high investment into the thing they do, for experts or power-users. For them it works.

So IMO the key question is how to find motivation or time or money to solve someone else's problem, without being forced to maximize the money-making part. Because by now we can see exactly what happens when money is the primary goal. Everyone starts with good intentions (solving a problem), but the incentives are so powerful. If you don't follow them you'll start to struggle, long-term, or get out-competed by someone who maximizes the money-making part of the job.