From what I understand, one cannot use XmlHttpRequest (and thus .ajax) for cross-site script requests (for security reasons), but one can use <script> tags and jsonp.
With 1.1.4, however, it appears as if jQuery silently ignores <script> tags that reference scripts in another domain. I've created a simple example html file.
var url = 'http://dl.dropbox.com/u/54081/simplealert.js'
$('head').append('<script src="' + url + '">')
alert call, so one can tell if it was called or not.
If I understand correctly, this means it is not possible to implement JSONP in jQuery 1.1.4.
There's no mention of this behavior change in the release notes, and there are no longer any tickets under bugs closed for 1.1.4.
Is this limitation by design? I understand this may be closed as won't fix, but I wanted to be sure to capture the issue so it's documented somewhere.