Patented hardware architectures
Unless you are a patent lawyer, then stay as far away from patents and patent research as possible, because if someone does slap you or your company with a suit, then you can be hit with triple damages if you are shown to have known about the patent.

So rule 1 about patents: Never actively look at patents.
A good second rule is: Never tell anybody about patents.

I guess it's a "don't ask, don't tell" sort of deal.