OP_RETURN was a new feature on top of the Bitcoin blockchain and soon businesses uncovered its potential by starting to develop services using these free bytes. Companies such as Proof of Existence, CoinSparkwere and even Counterparty were able to use it to offer notary, messaging, and security services. Currently, VeriBlock is one of these companies offering services using OP_RETURN but is now being hit with a wave of criticism as many consider the startup to be using OP_RETURN to flood the Bitcoin blockchain with spam.