Was a bit of a startling thread drift.

Call it a register or something else, regular checks by people at risk seem a very good idea, and should be encouraged. Compulsory just isn't practical, and wouldn't be effective, so there's no real point in arguing about whether they could be justified or not.

The assumption you can draw a clear line between "responsible" and "irresponsible" is pretty questionable. In all aspects of life most of us are responsible some of the time and irresponsible at others. So voluntary testing shouldn't be dismissed out of hand. Of course it already happens, but there might be things that could facilitate it.