@MattChambers IANAL and am green to much of this (hence the "dumb question" / "standard definition" toot).
That said, from the article: Howey v. SEC (1946) and the Howey Test:
[T]he court found that the plaintiff's sale of land and agricultural services constituted an "investment contract"—even though there was no trace of a stock or bond.
This case established the four-prong Howey Test, which states that an investment can be regulated as a security if:
There is an investment of money.The investment is made into a "common enterprise."The investors expect to make a profit from their investment.Any expected profits or returns are due to the actions of a third party or promoter.No contract requirement.
"Efforts of others" might presumably be, say, "enhancing the value of the cryptocurrency ecosystem" (I'm positing language a crypto-advocate might use, not my own), and transactions of others of those assets themselves, creating a putative market capitalisation.
Edit: Markdown glitch, enum. list.
@molly0xfff