No conceptual sybil protection, that is; the scheme they're using - see the "Contracts" tab on ES - is plain opt-in; sybil protection is impossible here.

As one would expect, someone's creating a massive number of keys, funding them with dust, and calling in to mint the tokens.

So if you're wondering "Why are transactions so expensive?" - that's 20% of the pressure.

P.S. Oh, and it has the ear-marks of a re-entrancy bug.

P.P.S. To the ones doing the bulk minting: it's possible you could be saving gas by using contracts (or even - plug! - a transient program) instead of the fund-mint-transfer three-transaction cycle.

This is just a guess, and definitely requires prototyping. I won't be doing it on a sunny Saturday, so take with a grain of salt.

ELI5: https://www.reddit.com/r/ethereum/comments/bvkvuz/using_20_of_all_gas_atm_an_airdrop_contract_with/epqlgy3/