Steve shaw described his shipping woes with this bike:
http://www.wooljersey.com/
I have shipped more than 200 bikes between Italy and the US and have never had such bad luck, especially when dealing with the post office.
Unfortuantely, if you plan on riding the bike, you will almost assuredly need to replace the derailleur. Had the face plate of the derailleur not been of the drillium sort, you could likely have done something to receover it, but once the face plate has twisted as much as what you see in your photo, I believe it will be very difficult to sort out.
As far as blame for the problem, I believe that this lies squarely with the seller. The seller should have removed the derailleur if the rear wheel was removed for shipping (the chain should also be removed or taped in place). The dropout spacing should also be protected with an appropriate spacer. As far as how to go about getting a whole bike, I would suggest a simple straightforward and factual email to the seller. No accusation, no demands, just a simple statement with a request for the seller to make his feelings known. Most honorable sellers will go out of their way to try to make the buyer whole, as long as they are not confronted with an angry and aggressive buyer. Ebay will not do anything in this case, nor do I think will paypal.
Should you need any Italian translation help in dealing with the seller, please let me know offlist.
Steven Maasland
Moorestown, NJ
USA