Long tail risks makes avg/var/standard distribution stuff useless. Best measure here would be the median income (50th percentile - or the 50th person out of 100).
Same thing with wealth distribution and taxes - averages are pointless since 1 rich guy + 99 poor guys will have an average of ~1/100 the rich guy (which is still a lot of money) - even though the poor guys have $0 in assets (usually negative equity because of debt).
The median of that distribution would be $0 - hence providing a better representation of actual probabilistic income/taxes.
I'm absolutely with you; I would love to see more data on this.
That said, while we definitely exist in a "hits" driven culture, I expect such hits would be boundary crossing, and I see no reason to presume a middle class can't exist in any given boundary. (Or, maybe, it could grow toward that.) I'm reminded of the recent post on Pandora talking about "middle class musicians".
I'm really curious to see some more data here, I have a feeling that the disparity is severe.