It happens at UPS also, along with everybody else unfortunately.
As far as getting signatures, I have seen where Fed Ex has left parcels on my doorstep with out a signature. I can't speak for them but trust in what your are saying. As far as UPS goes, if the shipper specifies a signature then the package is to be signed for. If there is no specification or required signature then it's up to the driver to release the parcel.
Oh BTW J_hallgren, when you deliver 14 million packages per day then talk to me
I would like to hear the other side of the story though and from what it sounds like there is another side to it.