I haven't participated in any, but it is good  that I read this thread. It gave me good insights on this new Airdrop way. I also agree that if someone is asking for you to give them money or tokens first then it is a scam or they are phishing for your information, the air drop that I participated is free and as all airdrop should be, we help spread the word and in return they give us shares of the new coin that is what an airdrop for me is supposed to be.