Dan Riehl says it's the spending. So does Betsy.

Glenn Reynolds calls them, in the Wall Street Journal, a "they're really a post-partisan expression of outrage."

Michelle Malkin talks repeatedly of "generational theft", as in people are protesting robbing our children to pay for the current generation's mistakes.

MaxedOutMama brilliantly discusses the economics of things. The Tea Party folks, myself included, might not understand the details, but the principles of things are clear. She says here:

But with employment declining, and CRE busting so badly, and with corporate profits in a profound swoon, the fundamental economic choices facing a government are:

The government lets the natural economic cycle run its course (and that natural economic cycle is for a depression-like event), or
The government intervenes to bring needed infrastructure investments a few years forward, which puts a floor on the drop in economic activity, supports employment, and knocks the bottom off the cycle.
Our current leaders in Congress seem to have chosen yet a third way to produce a lengthening and deepening of the natural economic cycle, which is to pull money out of the private sector and to invest it in projects such as research grants for non-viable energy production, mandates for utilities to spend on higher-cost energy production, investments in frilly socially attractive programs (community outreach?), and throwing money into non-viable financial institutions. These steps pull money out of gross private domestic investment instead of supporting it.

I don't think it makes Americans extremists because they see the implications for this government mess. The protesters are protesting a tone-deaf government, bailouts, spending, and just the implications for the future.

Some aren't protesting at all...and taking a vacation.