facebook/react — pull request #359 by SanderSpies (2013-09-18 23:05:34+00:00)
Title: Give the user a warning when using unoptimized JSX code

As discussed in: https://groups.google.com/forum/#!topic/reactjs/5anr4Oxs8tA

Implemented it for all the situations whereby text/jsx is used - not just synchronous loading as discussed in the group conversation.