Do you honestly believe that closed source could never be polluted by stolen code? Do you believe that users of closed source products are somehow exempt from laws which could potentially affect open source users?
Certainly not, but if/when these instances occur, their damage to the market is much more easily calculated, making it subsequently much easier for proper restitution to be made back into the normal business community.
That may be a little hard to follow unless you admit that Linux is not a normal 'business', as they have nothing 'for sale', and most importantly to this point, that no one 'owns' the entirety of Linux and therefore there is no accountability.
What they do currently have, despite no accountability, is the ability to take privately owned works and redistribute them within new compilations of Linux to the world as 'free', as well as provide the source code along with a promise that it can be freely used and modified and even copied without return cost as well. This results in any code that is illegally GPL'd, which Torvalds himself has admitted can easily happen, to multiply it's usage unfairly, which is difficult to track, and leaves the affected 'victim' with little recourse other than to sue the possibly lone coder who put the trade secret in, and who in most cases would not be able to provide equal restitution, IBM in this case being an exception.
So in a nutshell the GPL multiplies the damages immeasurably, and there is no accountability to seek restitution. ("everyone" being allowed to not only use it but to "own" it illegally (modify, distribute, etc), instead of just one company doing so).
Again, thanks for your post, and hope you are enjoying your time away.
If it's a "lone coder" that ripped the source, that lone coder could just as easily post the source on USENET, IRC, FR, etc. In either hypothetical scenario, the victim is unlikely to receive full restitution for their loss. If a "lone counterfitter" prints an unknown quantity of $20 bills, do you plan to jail everyone that unknowingly accepted and passed those bills -- and how could you? It is probably best to keep your source code and plates secured, because robbery is a truly unpleasant experience. That's why the word "victimized" is often used to describe the situation.
Ya know, when I saw all your replies to me, I thought maybe you had discovered some evidence of code ownership. Imagine my dissapointment when I discovered more hypothetical, opinion, and FUD. I really don't have time to debate the potential consequences of hypothetical crimes. Ping me when some evidence shows up.