Without fees, how will the stellar fork cope with DDoS attacks?
Fee systems are integral to all other blockchains for a reason, without having some sort of fee system per transaction the kin blockchain will be prone to DDoS attacks.
A company (FaceBook) could easily have a bunch of grey-hat employees who swap their white-hat in their 9-5 for a black-hat in their spare time. Someone could easily write a program that creates millions of kin wallets, sends a fraction of a single kin token to each wallet, then start swapping those kin fractions amongst each other.
It would be easy for FaceBook script kiddies to scale this attack up programmatically and distribute this bot-net globally in such a quick amount of time that you could saturate the network. KinFoundation would have no way of stopping the attack without shutting down the entire blockchain.
There needs to be some kind of fee that would eventually cause such a bot-net to run out of kin to prevent such attacks.