User blog comment:DaNASCAT/Technical Update: September 9, 2015/@comment-25801460-20150910214518/@comment-126761-20150910220945

In general it is bad practice to use images from other sites - in some cases it would be termed bandwidth stealing, but even discounting that, putting your images under someone else's control is not a great idea. That being said, it wasn't a case of "we should restrict this ability", but basically "this is a natural result of the security changes".