In the cases described at that link, "the investors were required to sign up with the issuers' web sites and disclose valuable personal information in order to

In the cases described at that link, "the investors were required to sign up with the issuers' web sites and disclose valuable personal information in order to obtain shares. Free stock recipients were also offered extra shares, in some cases, for soliciting additional investors or, in other cases, for linking their own websites to those of an issuer or purchasing services offered through an issuer." The airdropped tokens I've seen did none of those things. Someone simply created a token contract and granted initial balances based on the ETH balances of existing addresses. The new owners don't even have to know the tokens exist.