I'm not sure I get you, I find this service most useful for public-facing SSH services (where the risk of attack in the greatest). I wouldn't bother forwarding my laptop's port 22 just to test it, that's for sure.

If an attacker wants to gather a list of vulnerable SSH servers in the wild they just have to map a bunch of random addresses (and that seems to be extremely common judging by the number of failed auths on my public server). Although it could be useful if you wanted to get a list of ssh servers not running on port 22.