Programming

Fully agreed, though I must say this, if you truly believe in the spirit of free software and, let's also be honest and add, can afford not to bend for the convenience of others (maybe you get funded through donations and/or grants), then you have the opportunity to make a piece of software so good, be it application or library, that it'll be hard for competition to come up with something better and proprietary, that's how it is for those instances where companies were sued for using them and not providing the source, e.g. Linux and John Deere is the last I remember.
It is that nature of copyleft that the more it spreads, the more it will enable for a culture shift, when people are faced with the inevitable conflict of the idea of keeping everything behind closed doors and not being allowed to if they want to take the easy way out, they might give it an actual thought or they'll try to be unfair and use without giving back, showing their true greedy colours. I'm not a purist by any means, as much as I'd like to, but that is the kind of world I'd like to live in