iCloud Activation Lock Removal

Hi All,
I came across this site:  iCloud Unlock Service
It offers iCloud activation lock removal. I am just curious if it actually works? I was under the impression the activation lock was fairly foolproof way to make an iPhone useless it it is lost or stolen, but if you can pay a few $$ to unlock it, then that means it is pretty useless?
I also thought that the activation lock was something implemented in iCloud servers, so Apple should have complete control of activation locks. If this site can unlock activation locks, why would Apple allow them to do that and thereby compromise value in the activation lock feature they offer?