No, they definitely do check for prior art. The problem, as I understand it, is that they don't cast their net all that widely, and how they do cast their net

No, they definitely do check for prior art. The problem, as I understand it, is that they don't cast their net all that widely, and how they do cast their net doesn't really correspond very well with the way most informed people think about such issues. In all the cases I've seen, they've cited other patents as evidence of prior art, where the other patent is pretty obviously similar (lots of the same keywords etc). On the other hand, stuff that's so incredibly obvious and widespread that nobody never even considered patenting it before might get through easily, 'cause you know, no prior patents... >< [I have a Japanese patent, and an attempt to get the same patent in the US was rejected by the USPTO (after years of back-and-forth...) because of prior US patents.]