I think it was AutoCAD that had the most diabolical dongle of all. Some ancient version of the software would seemingly work without the dongle, leading cheap offices buying less licences than installs and plenty of architects installing them on their home computers. Everything seems to work fine, except every save a tiny fraction of a decimal far far away is off. Way too small for anyone to notice. Until they have been working for weeks and months on a project. And then and only then do they realize that all the lines have been slowly drifting apart.