Number 4 is definitely one I agree with. Airdrops and the like cause a lot of spam to this forum. I'd also suggest that you don't participate in icos unless the developers are well trusted or the source code gets released and looks worthy of the amount per token that the developers/marketers are asking for it.
You are right but we can't stop the airdrops as ICOs start an airdrop to spread their tokens so the holder of their token will increase. I did join airdrop but when I checked it I can't even earn money from it as it will only cost you transaction fee for the airdrop token you want to sell that doesn't even cover your fee.