There are legitimate lost pet services and some that are not legit. Carefully research all companies that offer this service before signing up. Check with the BBB. Be comfortable that they will provide the services that they offer.
Scammers scan newspapers, Craigslist ads, and other Internet sites, searching ads for lost pets, then telephone a target with a sympathetic pitch, offering to locate the victims pet for a set price. Once you agree and provide your credit card you will not hear from them again.
Refer to the following websites for more information on the scam.
PetAmberAlert at http://www.petamberalert.com/blog/watch-out-for-lost-pet-scams/
ScamBusters at http://www.scambusters.org/petscams.html
Visit PGAAs Lost Pet page for help in finding your lost pet.