I don’t know about the experience of others...but just this last week I experienced a feature I intend to investigate further: Anybody else run into this?
I programmed my ADSB-out to enable “anonymous” mode when squawking 1200.
This concept was, if I understand it correctly, developed to allow a person who wished to preserve their “privacy” to fly about in an ADSB environment without revealing their identity. An example of a concern that promoted this idea might be a businessman who operates a small plane ...(certainly this doesn’t work if IFR flying a corporate jet above FL180)... to fly to a meeting with another entity and not reveal the operation of that small plane to a competitor who might ingeniously discern the business-purpose of the flight to his own advantage. Or it might allow a pilot to visit a girlfriend and deny his wife the ability to track the flight.
In any case, I have doubts of the validity of that “anonymous” mode because I am quite certain the authorities have the ability to know which ADSB transmitter is assigned to which airframe and that national security forces can not be deprived of the identity of the operation....nor can FAA who likely has not abandoned plans for a “pay per flight” ATC system might some day be implemented.
However, a problem I’ve noticed is that my ADSB-IN receiver can no longer distinguish my own 1200-squawk from itself. There always appears to be another airplane “shadowing” my little airplane-icon moving across my track.... and last week that little guy was about 400-500 ft below me.

It was very distracting.
{By the way, in a side-note, the altimeter setting was 30.42 which is commensurate with a lapse-rate of 500 ft. Upon landing at Blairsville, GA the friend meeting our flight handed us a print-out which showed our progress conducted completely at 6000’ when we actually cruised at 6500’. This seems to indicate the ADSB system was replicating a standard 29.92 mode C rather than the corrected 30.42 to 30.43 settings given us by ATC.}. This was very distracting throughout that flight-leg. However on subsequent legs the “shadowing aircraft directly beneath us” did not appear...perhaps because we had entered a different ATC sector..??
When squawking 1200 the little airplane icon on my moving map has ??? Displayed instead of a registration-number... and it does that with other 1200 aircraft but showing their altitude. When using an assigned txdr code we disappear as an ??? Aircraft and we are shown only as a tiny airplane icon..(this makes perfect sense because my ADSB is programmed to “ignore” my own tail number,...but when squawking 1200 it cannot distinguish it’s own squawk as being itself)....and other aircraft operating on assigned squawks show their Nnumber and altitude in conjunction with a symbol of > pointing the direction of their flight.
I find it distracting to continuously see myself as a nearby collision-hazard and (since I believe per my previous remarks I’m not anonymous to anyone important but myself) ...I plan to re-program my ADSB-Out to disable “anonymous” mode...and no longer have to deal with a ghost shadowing myself.