In the Bitshares system the zero fee transfers will be limited by how much BTS you have in the system. For example, if the network can process 100 tps and you own say 2% of all BTS, then you will be able to transfer as a rate 2 tps. If you go over that then fees will apply. The fee price will then scale dynamically the higher you go over your 2 tps threshold. Think of it like a time-share. The more shares you have, the more bandwidth you can use. So unless you are running some majors trading bots, this solution will work well for all users.

The reason this can work ob Bitshares is because is also a Decentralize Exchange which make earns fees from traders.