Patent Troll: a company that obtains the rights to one or more patents in order to profit by means of licensing or litigation, rather than by producing its own goods or services. "patent trolls are quashing the next, nascent wave of tech innovation"
Patent Trolls should worry most technology companies. They produce nothing of value (basically parasites) but seek rent from companies that do - which could be your company. In a many cases the patent(s) in question has been invalidated (unpatented) and in other cases the patent trolls backed-down if the tech company put up a legal defence.
Much has been written about this, but this might be of help to anyone fighting Patent Trolls :-