When it comes to cryptos, it's all about transparency and fair distribution. An ICO can be a ponzi scheme, and airdrop can be a ponzi scheme, even a PoW coin can be a ponzi scheme, when the coin is instamined.

There are airdroped coins with terrible distribution, like NEM and Clams. And there are coins with a distribution much better designed, like Byteball. And some people forget that Decred also had an airdrop phase.