I think someone else posted about this last week. Personally I wouldn't go through a third party. IF someone finds your drone I think they would be much more likely to contact you directly if you had your information inside the battery compartment. What if someone finds it that isn't tech savy? If they see your name and they cared about getting it back to you, they would feel a connection with your name and not a website. Most people that would find it would have no clue what that registration number means so I don't think you would have a worry about someone using it.
Personally I tag my drone with my registration number right on the outside. Reason being is I get a lot less flack from people who come around watching me fly if they see the registration number and I tell them it is a registered aircraft. I have a commercial registration so my number is tied directly to the serial number of my aircraft. Why pay for a tag and hope that someone will return your drone using a web link, when you can put a free tag inside with your name and phone number and probably get much better results. I have already resigned myself years ago that if my bird went down and I didn't find it myself, that anyone else who found it would chunk it in the trash or probably not return it anyway. I used to have better faith in humanity but now days not so much so.
