I mean, scam is kind of harsh, especially since you don't invest any of your own money.
I have gotten at least 10 different airdrops in the past month, one of them is worth 250$ as of now, the other 9 haven't hit the exchanges yet.
Literally free money. Could be beer money, or if you get lucky, you can re-invest the profits into coins you believe in.
No harm in pasting your ETH address and hoping for the best. The worst case, you get nothing, which still doesn't constitute as a scam in my opinion.

Though i would suggest staying away from ones that ask for donation in order to participate in the "airdrop". Those most likely are a scam and you probably will lose your money. They are rather rare though