I started seeing this phenomenon just this past year. Many DD's are now placing their iced drinks (which come in plastic cups) inside styro-foam cups as a general practice. I really don't understand this one on many levels. Even if they are not thinking of the waste, they must recognize the extra cost involved. It really bugs me.
I guess the idea is to keep the drink from sweating. Just ridiculous. At least take two seconds and ask the customers if they want one.
I started a group specific to this issue on Facebook. Though I have no real experience on how to raise attention or actually DO something about it, it felt good to vent and let even just a few people know about it.
Here's the page:
http://http://www.facebook.com/henway?v=info&edit_info=all&ref=nur#/group.php?gid=80465401614
Would love to hear ideas on this.