I too read the Flight article - and it really pi$$ed me off.
The article glibly stated that there would be an "incentive" to fit Mode S ..
Ooh, bet that got you excited ... well, that "incentive" .. ? You wouldn't be able to fly VFR !!
Let me make this clear from the start - I have worked as a licensed controller at many units (area and airfield, military and civil) - I do not support the mandatory introduction of Mode S.
It seems to be a pet project of some people (ex military fighter controllers I hear) that want to make a name for themselves.
These seem to be people who have no concept, understanding or sympathy toward General Aviation.
In fact in my experience Fighter Controllers have no concept, understanding or sympathy toward Air Traffic Control either !
Mode S may be a great success in the London TMA, and credit to those who have worked on it there,
but as far as I see it ... if you fit transponders to ALL flying machines you will probably over clutter many of the other radar screens around the country .. for what ? If everyone that decides to get airborne then decides to call ATC for a service .. do you really think the system could cope ?
Free airspace outside CAS should remain just that. In fact you can currently operate in Class D airspace without a transponder (on standard entry/exit lanes) and it works very well.