Bad UI is bad UI. Could be web 2.0, could be an app, could be web 3.
Have you seriously not heard about using different browsers for different accounts on the same site ? Many Androids will even let you install the same app twice to use different credentials.
So basically, a lot of software is badly designed, coded, and unsafe. Yep. And apparently people are trying to blame "the web" for that ?
BTW, there's no way to navigate your blog now ? That's good design ?