The governments or at least US SEC is not successful in regulating ICO in 2017 and they are late in filing cases and they are just ramping up their litigations this 2020. And besides they have Hester Peirce, which is a pro crypto, so I doubt that they will ran after this DEFI hype for now.
And what they are after right now is that those ICO who misinterpret their fund raising, they are after who run an security based on their definition. So unless they categorized DEFI as security then I doubt that they will go after it.
With governments capable of doing anything, I wouldn't be surprised if they ban people from using "De-Fi" services in the future. Or at least, they'll implement heavy-handed regulations that will stifle the growth of this emerging industry in the mainstream world. As far as securities go, I think that "Yield Farming" with their respective tokens qualify as a security. After all, people are investing in a platform's specific token to earn rewards in the long term. It's similar to earning dividends on the stock market. While it's hard to enforce regulations on "De-Fi" platforms, the government could easily hold developers accountable for their actions. They could fine the developers of such platforms by not complying with KYC/AML regulations or securities laws. There are so many ways that governments could put an end to scams in the "De-Fi" space limited to their own imagination.
Believe me, if "De-Fi" becomes regulated like ICOs, the growth of the industry will slowly decline. At least, you'll be able to access these platforms thanks to the decentralized nature of Blockchain technology. But things will not be easy, as governments will be on your tail following every action or move you make in the space. If you're a "De-Fi" platform developer and get caught, you can face fines or even jail time by not complying with fierce regulations imposed by the government. Consider what happened with EtherDelta's founder, and you'll see what I'm talking about. Just my thoughts
P.S. It seems that governments are concerned about the "De-Fi" craze. More info about that here:
https://cointelegraph.com/news/regulatory-risks-grow-for-defi-as-a-money-laundering-haven