Earlier quoted context omitted.
This alone doesn't explain why couldn't they leave the "super node" infrastructure in, with an extra bit of code ensuring mobile users are never designated as "super nodes". This way, quality would remain the same for the desktop/laptop users, instead of being degraded for everyone.
Not to mention that supernodes, though fewer in number, could still help reduce latency for those on mobile.
- asymetric links (ADSL)
- WiFi
- usage-based plans
- people shutting Skype down on varous occassions,
- suspended laptops,
- bandwidth competing applications (video).
I remember past Skype had lot of quality issues, sometimes connection was very choppy, dropped unexpectedly, or took long time to establish.