I have a useful little cable I got on eBay, which basically looks like a very short USB extension lead with red plugs. It only has the power pins connected and the data pins are deliberately not connected. Very useful for parasitically charging off a computer without it trying to establish a data connection.
I bought it so save the annoyance of a computer trying to make a data connection when all I want to do is charge the phone. It never occurred to me that it may be a hardware firewall. Don't tell the seller or they'll double the price. :o)