In fact the GPL won't even "steal" anyone's IP at all. If the person "stealing" the GPL IP doesn't live up to the GPL, then it's a garden variety copyright violation, same as if the person "stole" Sun's or Microsoft's IP.
According to 99% of Linux fanatics it does. Just like when SCO unknowingly released a version of Linux that potentially had IP planted by IBM.
I put "steal" in quotes for a reason. It sounded like that to the person I was responding to, any loss of control of your IP or movement of your IP into the open source space where people could use it without royalties is somehow theft. I don't agree with that definition, thus the quotes.