This brings up a good point. The two companies I've worked for have used a ton of open source software and have contributed nothing back. It kind of disgusts me. Am I wrong to feel that way?
If they want to give up the intangible benefits they would get from sharing those changes (at least the non-business-strategic ones), that's disheartening, but I wouldn't lose any sleep over it.
In my case, I started feeling like I was working for a parasite. And... I didn't particularly want to continue working for a parasite.