ADS-B In/Out could serve perfectly, if not better, than Flarm, BUT physics comes right at the corner. The US already had to introduce UAT to free available bandwidth from 1090ES and if we really would all go for an ADS-B 1090ES solution, the gibberish of all that stations will congest the air. Flarm did overcome some of the restrictions by reducing power, so making the area covered "fit for purpose of the gliders". Now with the new PowerFlarm the advantage gets less ... Same trouble as with radios, as long as we all had 3 to 5 Watts of power, we could reach the next airport and traffic control, now we blow our stumbling with 16 Watts from final in Birmingham to the Orkneys.