@limer I read your article on http://www.popularmechanics.com/technology/apps/a25956/mastodon-twitter-open-web/ and as a proponent of an open web, However:
* You assume that [any !OStatus instance] has the responsibility to verify its users.
The fact is that each user has their own responsibility to verify their accounts. Say, for example, that you are you. Then you have a personal website or work account. At this profile, you place a link to your social account (just as with your Twitter account). Noone else can fake that (assuming you're not hacked, but that's a different story).
Furthermore, there's something called !indieweb which makes this verficiation seamless and integrates into browsers etc, where if someone claims to be someone else - so called rel="me" links can be used in a sort of "callback verification" scheme. Fully automated with green checkmarks and whatnot.
All other issues you raise are also issues on the web in general.