Z:gnu-www-ja-software-patents--68b21d-Because of the expense, it is/en

Because of the expense, it is often out of the question even if you can find solid prior art that ought to be sufficient to overturn the patent. As a result, an invalid patent, a patent that nominally shouldn't have existed (but in fact lots and lots of them do) is a dangerous weapon. If somebody attacks you with an invalid patent, that can really cause a lot of trouble for you. You might be able to bluff them away by showing them the prior art. It depends upon whether they can get scared off that way or they might think &ldquo;well, you are just bluffing, we figure you can't really go to court, you can't afford it so we'll sue you anyway&rdquo;.