facebook/react — pull request #1788 by kimagure (2014-07-04 03:07:32+00:00)
Title: Added check against the use of the same ref multiple times

Using the same `ref` multiple times can cause some pretty weird things to happen (usually resulting in the last component using the `ref` to be set for an owner's refs) as discussed here: https://github.com/facebook/react/issues/1782