Airdrops are not a new tactic. Since the 90s some companies have used the tactic to provide stock as rewards for marketing or other efforts. The SEC cracked down on those where the security did not follow the rules.
See the press release from 1999 where they cracked down on 4 cases where the stocks did not follow the rules:
https://www.sec.gov/news/headlines/webstock.htmThe bottom line is that it is imperative that you follow the rules, with respect to investor rights and ensure your coin truly is a token. If you do that, airdrops will be protected. If you don't, you provide reasons for the SEC and the CFTC to come after you.
That said, airdrops should be an area of caution. Just last month, Rise and Bittrex had to unwind airdrops because the way it was handled violated SEC regulations, and they had to halt their airdrop to stay listed.
https://steemit.com/cryptocurrency/@fruitdaddy/is-this-the-end-of-air-dropsUsing airdrops or even the sale of a token before you have actual utility of that token is a red flag, and will likely get you one of those new subpoenas the SEC seems to be handing out. I suggest you talk to your lawyer before you do an airdrop, and review the marketing materials and promotions to make sure you are covered.