I know it's recommended, but in the past (before composer), working with Zend Framework and the like, EVERYTHING was included (except certain temp or CMS files and folders), including any vendor folder.
This honestly this made versioning easy, in the sense that if we moved servers or had to reinstall on a prod/qa/dev computer, we didn't have to hunt down the correct versions, and allowed seeing easily what was actually changed there even when (gasp) customizing code in those folders (which I'm against anyways).
So, moving forward, on a team that's new to Laravel and composer, is composer really good enough when installing/uninstalling/updating/downgrading on prod/qa/dev environments, or is there too much risk in losing code or changes or time by ignoring all of this source code in the vendor folder and simply relying on composer to "make everything right" if something has to be reinstalled/reverted/updated?
EDIT: Here's an example of our current .gitignore file, tailored to Laravel Mac PHPStorm basically:
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