I bought Oshkosh up as an example of just how succesful see and aviod can be. Oshkosh airshow has more VFR aircraft flying in an area not much bigger than the Caloundra - Redcliff CTAF, then Australia has aircraft.
Numbers per se don't make for traffic problems. It's more to do with the mix of operations and aircraft types.
30 cessna singles arriving in trail from one direction is no problem. A microlight in the circuit with a B737 inbound conducting a practice approach mixed with various other arrivals and departures is another matter.
It only takes two to tango!