So, while my approach to research on reactions is limited to my reading comments on photography sites I frequent, the overwhelming response to this news is "deleting my account now." Why is that?
Well, it is going to be a result of the rather casual care for copyright previously exhibited by Chinese corporations in the past. The simple fact on that is that they simply haven't cared and have ignored any attempts to enforce. That doesn't leave photographers with a warm and fuzzy feeling about this acquisition, especially given the Getty comparison and the lack of love that name engenders as well. Long story short, I don't see a there being a stampede to join 500px now, but I definitely see a stampede leaving it.
For those looking to shut it all down, bear in mind that you never really, actually, leave the site. It's a bit like the Mafia that way, once a member, always a member. Nevertheless, my suggestion is delete all your photos first, then delete your account. Is that perfect? Not really, but it will prevent any further additions to the site, so you minimize the total impact to you over time.
If you're not looking to shut down your participation, my advice is to watch for some time. If nothing else, you can gain a sense of where the site is truly headed and whether or not you want to stick around. That may take some time, so it's up to you, but doing this may be the middle ground on reaction.
As for me? I shut it down. I was barely using it anyways and, well, I'm actually more irked to see another Canadian company sold off than anything else, especially for a song. $17 million? That's not about the platform, that's entirely about the content. Moot point for what I had already posted, but that will be the last of it.