There will be two new application sources:
1) The Application Center (which is what y'all are talking about) is on-device, and contains carrier-specific choices. You don't have to use it.
2) The Application Storefront will be run by RIM, giving an 80/20 split with developers, support Paypal, and is usable by anyone. Carriers can't stop you from downloading from there.
Even if they did, it doesn't stop anyone any more that it stops WinMo owners from downloading such apps.... because you're NOT tied to what RIM or the carrier makes available.
Again: Consumer Blackberries can download and run any app they want, from anywhere they want. (Corporations can control the ones they own.)