There's always a danger that you'll introduce a bug in your code at some point, right? If you 'pull' from a lot or sources, at some point one of those sources will introduce a bug. But if you have a lot of high quality committers (book authors) and you continue to pull (read) from those sources, you stand a good chance of discovering and squashing these bugs eventually. In fact, as your code (mind) matures, you start to develop procedures to test unproven pull requests (theories/ideas) before merging and committing. You'll be especially careful of unknown authors or authors that have introduced buggy code in the past, while possibly giving full commit access to authors you trust.