Why? I'm so glad you asked. To protect them from dog-nappers? For research purposes? Nope. The DNA profile will be kept on file so that unclaimed dog poop left on the property can be collected, sent to DNA Pet World, profiled, matched to the offending dog. The negligent owner will then be required to pay a fine of up to $1,000.
According to the article, "Feces identification is a booming business. DNA Pet World and PooPrints - its motto is "Match the Mess through DNA" - are spinoffs from BioPet Vet Labs."
It's totally worth taking the time to check out the PooPrints site. Hilarious.
DNA sequencing is simply a technique that gives the order of nucleic acids (A, T, G, C) in someone’s (or some dog's) DNA. This is what the folks are paying $200 to do - get the code for their dog and have that code put into a special database for future use. Then, when a mystery poop sample is received, the same test can be run and the resulting poop's code compared to that database to find the guilty dog. If you'd like to know the specifics of how DNA sequencing works - check out this great Cycle Sequencing Interactive from the DNA Learning Center.