Using proxies is necessary for internet anonymity. The last time that I viewed a flash file, it knocked me out of my proxy, such that I viewed the website directly from my unproxied IP address. Flash can do that because it is a client-side object. I had therefore disabled the flash capability of my browser. Youtube.com's videos are in flash format. Any Iranian in Iran that views youtube flash footage might likewise be knocked out of whatever proxy they are using, such that the government of Iran (which monitors internet traffic) can see that they are viewing it. I therefore advise all Iranians making amateur videos of the government's actions to make them in downloadable .mpg or .wmv format.
While it's true that Flash objects can ignore proxy settings on the browser or system, the Youtube player did not, last time I checked. You can verify that by observing packets while buffering a video. (Again, last time I checked. It's possible things could have changed since then)