There are some collection of ERC721 tokens that will airdrop users tokens if they have proof that they own an ERC721. There are other ERC721 collection that will airdrop tokens to every holder of the token. If the user deposits the ERC721 token which is eligible for an airdrop into the Ocean protocol, and an airdrop happens, the Ocean will receive the airdrop instead.
Since the ocean contract does not have any way to withdraw random tokens, the airdrop will be locked inside the protocol.
Not sure about the recommendation, but take note that some ERC721 collections may mint tokens for every holder or may airdrop tokens to holders once in a while. Make sure that these tokens are either not accepted into Ocean, or that the users are warned beforehand that the airdrop will be lost.
Ocean.sol#L79
