This article doesn't really answer the question of whether the generics are safe. It is true that your veterinarian provides a service that box stores do not, but ultimately many consumers are going to be drawn to these lower cost generic alternatives. People want to know if the products will be harmful to their pets or not.
It appears that while the generics have gained regulatory approval, there haven't been any controlled scientific studies to answer the question satisfactorily for consumers. Products like Frontline have a long history of safety, but that proven record comes at a cost. If a consumer wants a cheaper generic, they will be taking a risk with their pet. This statement from the article did resonate with me:
"It's also important to note that the federal government has actually ordered multiple manufacturers of these generic flea products to remove some products from store shelves."
In my opinion, until more time-proven evidence is available, the discerning pet owner should probably avoid the generics. View Thread