Wall St. Sell-Off and the Big Banks

This week's Wall Street sell-off has me wondering: is Wall Street only about the big banks and financial institutions? That seems to be the major reason behind the sell-off: the big banks don't like Obama's newly announced tax on them.

My question is this: Isn't Wall Street supposed to be about more than just the banks? Isn't Wall Street also about the vast majority of America's publicly owned companies like manufacturers, service companies, telecommunication companies, high tech and software companies, etc? How well they are faring doesn't seem to matter. It's all about the banks.

Am I naive or has Wall Street indeed changed into a creature of the big banks and financial giants?