I think we will see the same as the loan advertisements in the future where the APR displayed has to be the rate which most punters will get, so instead of ADSL+ "Up to 24Mb/s" they will have to say something like
Average
Real
Speed (ARS 9Mb/s) or whatever.

But then if you are relying on BT wiring even ARS could be misleading, 512Kb/s max here, less than 2km from the exchange

thank God for cable.