Earlier today, I took a few minutes to package up some Ruby code that I wrote for my own use in order to share it under the GPL. I figured that a few people might find it useful.
Within a few hours someone who downloaded one of the packages sent me back some useful changes. (Thanks Pat!)
Another example: about 9 years ago when I got my first digital camera I wrote a Java utility (PicWeb) to recursively walk nested directories creating HTML with links to image files in the current directory and to subdirectories; it also generated thumbnail images. Not rocket science but it was just what I needed. Over the years, of the roughly 25,000 people who downloaded PicWeb, four people sent in very useful code for new features. Everyone wins.
I wonder how often companies waste money and other resources by trying to "protect their IP" and not taking advantage of open source development. Sure, some software needs to be proprietary for business reasons, but the decision of proprietary vs. Free Software should be an informed decision.