I mentioned a few weeks ago that I had found a package that was labeled with the recycling code #7 - other, but also stated that it was compatible with #5 - polyproplyene, and I questioned the validity of the codes.
Apparently it is a very real problem. The linked article describes a similar package being labeled as "PET compatible".
The article also answer a number of tacit questions that I previously had. Use of the recycling codes is governed by a patchwork of 39 state laws of varying content - clearly national standards are needed, as recycling of polymers is becoming more important all the time.
My heart goes out to recyclers out there having to deal with the dirty input streams.