The old way of thinking about authority was static and hierarchical. Seniority and rank are crude, linear, black and white tools. While they have the advantage of being simple and clear, even organizations that are thought of as being strictly hierarchical, such as the military, have long abandoned such simplistic thinking.
The Web has brought a new form of contextual authority. Mike Arrington has tremendous power in the Web 2.0 world. This is not because he has any great experience. While Mike is a smart guy, before he started writing TechCrunch, he was just another ordinary lawyer and entrepreneur. In the grand scheme of things, his background is no more or less impressive than Penelope's.
Mike gained authority because his writing ability (and hustle) allowed him to build a massive audience which trusts him to bring things to their attention. Ultimately, I doubt any TechCrunch readers care about whether or not Mike was successful in his prior life; what we care about is whether or not he keeps delivering scoops and insightful analysis.
(This post is part of a longer comment on Penelope Trunk's blog.)