Disclaimer: I am not a lawyer, this is not legal advice.
Second, one of the basic principles underlying patents is that you either
enforce them or lose them.
This is not the case for patent law. It is central to trademark doctrine
but the application in patent law is not fundamental.
It is possible to claim that a patent holder willfully failed to enforce
the patent with the intention of encouraging people to infringe it and
that by doing so the patent holder created a public license.
The contract structures by which patents are licensed but not sold
create a number of arguable defenses.
It is also possible to put the patent holder on notice and to force
them to defend a claim or loose it - a tactic which could probably
be used to effect by the Internet community to sink certain patants
whose holders pockets are far from deep.
The principle game with patents however is to use the threat of
litigation to extort payments. In the UK this game is illegal, as the
owner of a certain US trademark discovered when they attempted to
grab a domain name from a UK company and found themselves paying a
considerable sum in damages.
In the middle ages this type of thing was rife. I think it was
called barratry but the term has a somewhat more specific meaning
today. In any case Dante suggested a suitable damnation for such
folk.
Phill