The thing is that Copyleft is using the same legislation that corporations use to protect themselves. So spending a lot in lawyers for this might set a precedent that could backfire.
Also... I don't think there's a lot of incentive for them to do this, because if they have that much money they might as well just make their own software and have better control over it. Maybe use instead non-copyleft licenses like MIT, like Google sometimes has done.
It's very likely there are already many GPL violations out there that we'll never know about due to obfuscation or them simply being hard to identify, but nobody has the time, the money or the power to actually try and challengue a corporation about it and come out unscathed.