IOTA is an open-source distributed ledger (CRYPTOCURRENCY) focused on providing secure communications and payments between machines on the Internet of Things.
From Bitcoin developer Greg Maxwell:
I evaluated their technology myself, it isn't just busted: it is scam-grade over the top outright reckless nonsense. And their negligently busted hashfunction was trivially exploitable and we all got to see IOTA lie about their vulnerabilities in public (and continue to do so to this very day). Shameful. The main thing that prevented their system from being burned to the ground was its complete and total functional centralization.