When using Select2, filling a select box, and not seeing any result, chances are that you’re querying a different server, which requires CORS, which in turn isn’t supported by Internet Explorer (9.0 and below).
Using the jQuery-ajaxTransport-XDomainRequest plugin fixes
Explanations are in the README.
(this problem is of course not specific to Select2, but given the layers of
code/libs between the developer and the creation oFJthe XHR object inside
ajax() function, one might forget this detail like I did)