The udids have already all been hashed. It is the hashed values only that are stored on the site. The only piece of information sent to the site is a hashed udid (the udid is hashed on the browser before any information is sent over the wire).
The point is that in order to stop people from passing their UDIDs around the net they way some other checking services have made them do, this service does not have any of the original UDID's on local storage. Even if my site is compromised, it will not further the spread of UDID information.
Of course, you do have to trust that what I am saying is the truth. Anyone can choose NOT to submit their (hashed) UDID to my site.
FYI: you can get around the no reply box "feature" by clicking "link."