(... Chat-123.45, Air-Air-122.75, etc.)
It should be pointed out that 123.45 MHz (aka "Fingers") is not a "chat" frequency. It is officially designated for use in aircraft flight testing and transoceanic communications. But because of the increasingly congested 122.75 MHz Air-to-Air frequency, more and more pilots are using "Fingers" illegally.
Using 123.45 MHz over the United States or its coastal waters could potentially lead to a $10,000 fine. Since the FCC designated this frequency to be used solely for test flight communications, any other use constitutes an illegal transmission, and pilots transmitting illegally could be fined up to $10,000 for each transmission or taken to small claims court for damages caused by interfering with the data transmission during a test flight.
Legally, for air-to-air communications between private, fixed-wing aircraft, there is just one authorized frequency: 122.75 MHz. For general aviation helicopters: 123.025 MHz. Gliders and hot air balloons share 123.3 and 123.5 MHz.
BTW, for folks using 122.75 MHz in a practice area, others don't need to know every maneuver you plan on practicing. That takes up valuable bandwidth. Just let us know you're there and at what altitudes.
A few years ago I wrote both the AOPA and the EAA requesting them to lobby the FCC and the FAA for more Air-to-Air frequencies. I received a nice reply from AOPA but nothing from the EAA. More pilots need to lobby for additional Air-to-Air frequencies.