I read the Satoshi paper and there's zero mention of such exchanges, yet it appears a few exchanges now exist and they control the price via buy and sell orders, or am I wrong.
Any commodity/currency has to have an 'exchange' to refer to, I'm awar there are several, but I'm not aware of any list showing the major btc exchanges and more importantly the buy/sell orders in their system.
Maybe I'm wrong and Satoshi addressed having to have an 'exchange' or exchanges to determine a currency price, but I have read it a few times and I don't recall seeing Satoshi mention a currency exchange to set the price of btc in trades, in fact such exchanges are against his ideals, since they become centralized control of the currency.
Here's a couple nice sites to get you started:
http://bitcoinity.org/markets
www.bitcoincharts.com
As a friendly word of caution, make sure you diligently research any exchanges you intend to use.
Additionally, keep in mind Bitcoin is intended to be used in a decentralized market. Basically, it seems Satoshi assumed that Bitcoin could stand on its own merits and it would inspire others to help build a foundation around it. That foundation would include things like exchanges, a block explorer, this community forum, etc. There was no need to make specific plan or creation beyond the original codebase, and to do so could arguably be considered as contrary to the philosophy behind Bitcoin's purpose. So, yes, you are correct that this also applies to current, centralized exchanges, but a decentralized exchange may be on the horizon...
Basically, just keep in mind that its a small, rapidly-changing market and there are merchants and exchanges and services popping up all the time, so many that you might miss or not hear about many of them unless you spend a significant amount of time keeping up with things. Inevitably, many of these turn out to be duds, but through competition, the good ideas/exchanges/merchants stick around.