Which logical fallacy is used in the text?
I can't believe you'd hire Bob Humphrey to watch your dog! Did you know that his friend adopted a dog but then took it back to the shelter after just one week?

 - guilt by association: a negative association intended to discredit someone or something
 - bandwagon fallacy: the assumption that the popular choice is automatically correct
The text argues that Bob must be an irresponsible dog owner, because his friend was an irresponsible dog owner. However, even though Bob's friend was irresponsible, that doesn't necessarily mean that Bob is also irresponsible. This illustrates a type of logical fallacy known as guilt by association.