In theory the Patent Office is supposed to check for prior art, but in practice the Patent Office's budget has remained constant for the last few decades while the number of patents they had to deal with increased exponentially. At first this resulted in a backlog, but then Congress passed a law saying that they couldn't have a backlog. So now patents are subject to less and less scrutiny.
The unfortunate thing is that our other laws assume that the Patent Office is able to do its job - patents are presumed to be valid unless you go through the legal hoops necessary to invalidate one. And being in the process of going through those legal hoops isn't a defense when the patent holder sues you for infringement, so there's really little benefit for you to go through them in the first place.
The unfortunate thing is that our other laws assume that the Patent Office is able to do its job - patents are presumed to be valid unless you go through the legal hoops necessary to invalidate one. And being in the process of going through those legal hoops isn't a defense when the patent holder sues you for infringement, so there's really little benefit for you to go through them in the first place.