FFBob has it nailed. If you are operating under VFR then you have to ensure you are actually VISUAL. You can not expect a traffic service miles away dealing with multiple calls to 'see' better than you. If you choose to share the airspace with other users then you have to accept the responsibility that goes with it. It never ceases to amaze me when a pilot 'some distance' from a traffic unit calls up and wants to know what other traffic is in the area. He is not talking to a modern version of 11 Group ops room with plotters and controllers, but frequently a single person getting calls from as far as 40-50 miles away (IN ALL DIRECTIONS) many not with mode c and unable to accept a climb that puts them under IFR. The sheer 'radio time' this takes put an added strain on the 'service' and is UNREASONABLE.
Pilots have to realise THEY are in control of THEIR flight and have to share airspace will ALL USERS; frequently a better choice of route will put them in less congested area's and of course a clean screen works wonders.