Solution is in the middle ground. Companies should try to build platforms that open the door to prosumers without knocking down their own walls.
I think Apple has got this right. When its lead users started hacking the iPod with Podzilla, PodQuest and Encylopodia and jailbroke the first version of the iPhone, it did a bit of of commercial Jitsu, taking the force of the demand and turning it to its advantage with the SDK and iPhone apps store.
Here is perhaps the best example of the prosumption dilemma solved: Apple keeps control, appears open and adds value to its product way beyond what it could achieve alone through vast collaboration.