But it does add another example of why we should be wary of even well-meaning for-profit companies, without some kind of more solid guarantee that they won't sell out in the future. For stuff like this, either a nonprofit foundation, or at least a forkable open-source version of the platform, seem like necessary prerequisites if you want to ensure that Elsevier-and-co can't buy it out. I guess a company 100%-owned by a strong open-culture advocate could be reliable also, but it gets more complex when investors are in the mix.
Also a reason I don't trust academia.edu compared to, say, the arXiv.