I don't think I can be considered an open source advocate. But the basic premise of open source ideology (the way I understand it) is no limitation in any form or shape. When you buy a hardware (or software), you should not be subject to artificial limitations imposed by the manufacturer.
PS3 is a very good example IMO. It comes with very powerful hardware, which you paid for, but you are only limited to rules placed by sony. As a matter of fact Sony goes through a lot of trouble to make it almost imposible to do anything else with the hardware.
Similarly, I should be able to install any app on my iphone/ipad that is not approved by Apple without have to go through hoops of cracking the device.