I participate on Disqus, but only on economics and tech blogs. Effectively, I've compartmentalized my Disqus identity to a particular persona (not much different to my HN one).

I don't comment on any website using Facebook. Actually, I have FB completely blocked in my primary browser, so I never even see any assets served up by facebook.com or fbcdn.net etc. If there is a Facebook comment section, I don't see it.

It's a matter of identity and overlaps in facades.

In real life I behave differently in business meetings, in pub chats with coworkers and other people in the industry, at college friend meetups, at secondary school friend meetups, at family meetups. I'm effectively different people with different shared culture for all these people. Comments I make in one context will not translate, and in some cases may even offend, in one of the other contexts because it will rely on the culture shared with that group - especially when the culture was created when I was much younger.

This is why wider web Facebook identity is abhorrent to me, just as much or almost more so than Google+ unified identity. The straw that broke the back of Google+ for me was Youtube comments. When I couldn't leave a comment on a silly cat video without wondering if it was showing up to my business contacts, I deleted my Google+ profile so that I could break the link with my YT account. I couldn't find any other way to break the link, and Google+'s benefits, such as they are, weigh so little with me that I would, and have, give them up in a heartbeat in order to be able to make another pseudonymous comment on YT.

So the question to me is more subtle than non-mandatory Google+ integration meaning Google+ is dead. Non-integration of Google+ with YT is all positive, as far as I'm concerned. And more deeply, for people who live more of their lives online (rather than especially older relatives who mostly use the internet to keep in contact with family and close friends), the idea of a single unified identity for the internet is fundamentally a non-starter. So any move from Google to make it non-mandatory is actually the only workable way forward.

Facebook I avoid, not because I don't trust or use Facebook but because I don't trust various facebook-based applications not to post spam in my feed.

But disqus? Absolutely, for the reason I outlined above. Disqus does what Google Plus should - a unified commenting infrastructure that is not opinionated about how comment threads should be run or identity or whatever.

Disqus has a lot of weaknesses, but they're mostly bugs and performance problems. Google should have made a Disqus and then bolted it onto their Facebook clone.

Instead, they made a Facebook clone and perverted it into a Disqus system.

Personally I interact only on web sites where I can register with my email address. The sites you listed are those that I avoid more, I don't like knowing my comments are tight to my personal identity on a service that does also manage content. ie. I would be ok using an OpenID from a company that does only OpenId. FB/Google/etc. authentication platform is just a way to build up their userbase to make money out of user profiles (which is not necessarily bad, but I don't want to be a product just because I need to post in a forum).