Even random talking head has at least a bit more credibility than random twitter user.
Not sure I'd agree with you, there. They're journalists, they don't necessarily have any expertise in anything they are...punditizing...about.
The twitter thing is similar to the old "man on the street" interviews. As long as they're put in the proper context, I don't see it as particularly awful. The only danger is that they're subject to cherry-picking...but then, what news opinion isn't these days?