The point is PRIVACY is a major concern with Disqus and any of these third-party services. You lose control and leave your commentors vulnerable.

Here are some articles about it, there are REAL issues here to discuss:

https://www.redstate.com/2012/09/01/our-failing-disqus-experiment/

http://www.digitaltrends.com/web/top-100-websites-how-are-they-tracking-you/

https://addons.mozilla.org/en-us/firefox/addon/donottrackplus/reviews/464582/

http://www.baekdal.com/insights/the-first-rule-of-privacy

And some choice snippets:

"People understand that the Disqus widget is a commenting system, but it’s also a tracking system. It follows a user’s activities across sites that use Disqus, even if the user is logged out,” says Downey. The info collected by Disqus includes IP address, browser version and installed plugins, and exit links — data Disqus refers to as “Non-Personally Identifiable Information.” However, this information can be used to de-anonymize users, when combined with third-party information. And because Disqus reserves the right to share you data with third-parties, such action could be taken. Furthermore, says Downey, “Disqus has come under fire for privacy issues after it published its users’ full commenting histories on user profile pages that were visible to the public.”

And

"There is a blithe disregard for the personal privacy of anyone who uses Disqus. In the past if someone wanted all my comments they would have to register on the site, log in, visit my profile, and copy my comments one by one. Their alternative was to use Google to search for my comments. While my comments were open to view, my privacy was protected as it took a substantial investment of time. Why do I care? Because comments, used out of context, can be made to prove anything. If you think that using comments out of context isn’t a problem I encourage you to review what happened to Josh Trevino this week.

What Disqus does is give any other Disqus user the ability to “Follow” you. This means all of your comments, on every site you visit using Disqus, are aggregated for them. You do not have the ability to block “Followers.” So if someone is stalking you in the comments, every time you post a comment your stalker is notified.

Disqus refuses to acknowledge that the political blogosphere is populated not only by passionate activists but by a sizable cadre of vicious and stupid gits who think nothing of harassing your employer or SWATting you at home."

Scary stuff! And a good reason to keep comments and control in-house. It's not worth losing the trust of your users just for a few fancy "bells and whistles".