>"Any developer on your staff could look at something on line and derive some code from it, and drop it into your codebase"
Well that's what's so crucial about having solid Best Practices and hiring good developers. If you hire people who break the rules (deliberately or accidentally, with your knowledge or without), then there's your problem. The GPL has nothing to do with that scenario, it's you hiring people who can't toe the line.
I'll reword it for you. Well have a Special class. We'll pay an instructor to come in and give our devs a half day course on How not to Violate the GPL. GPL is another bureaucratic hoop to jump through, just like race and gender discrimination classes. Cost of doing business.
No, you need systems in place to make sure you don't commit copyright infringement. But if you do commit copyright infringement, there are solutions other than opening up your code, such as buying a license from the guy you copied from or removing the infringing code.
Well that's what's so crucial about having solid Best Practices and hiring good developers. If you hire people who break the rules (deliberately or accidentally, with your knowledge or without), then there's your problem. The GPL has nothing to do with that scenario, it's you hiring people who can't toe the line.