VFE makes the point that not using a transponder is not going to save you from being identified in the event of an airspace bust. The fact of the matter is though, that, of the four infringers of the notorious red arrows TRA ( as it then was known) Elvington bust in 2003, the only one who was actually identified and prosecuted was the hapless and responsible pilot who was actually sqawking his position (and identity). The other non squawkers got away unidentified and scot free.
The use of safety related equipment to mount prosecutions of this type is completely inappropriate. It is no wonder that pilots are apprehensive about mode S and switching the damn things on in the first place....