"I don't want to get involved in crypto if the regulator says it's not OK. I can't afford to be offside," Kevin O'Leary said.
The alonzo upgrade that rolled out on Sunday will now offer smart contract capability, according to the network's developers.
"There's no real reason... People are excited about it, and it goes up," William Quigley said of the altcoin surge in a Bloomberg interview.
Cardano's big "alonzo" upgrade rolls out on Sunday and will usher in the network's ability to run a range of crypto applications.
Solana's sol token rose by almost 40% to a record high on Tuesday, driven by an ongoing boom in demand for assets with DeFi capabilities.
"These platforms - whether in the decentralized or centralized finance space - are implicated by the securities laws," SEC chief Gary Gensler said.
Ether hit its highest since mid-May on Wednesday, swept higher by a wave of investors chasing gains in popular alternatives to bitcoin.
Poly Network has taken the unusual step of embracing the apparent hacker, who stole $610 million in early August.
The rise of DeFi adoption was mainly driven by experienced cryptocurrency traders looking to diversify their portfolios, Chainalysis said.
$33 million in tether remains frozen by the stablecoin's parent company, which Poly Network said it was working to restore.
At the current pace, total assets in DeFi will break $800 billion near the end of next year.
"We cordially invite Mr. White Hat to be the Chief Security Advisor of Poly Network," the company said.
High-profile investor Kevin O'Leary says one appeal of DeFi is that it could get rid of middlemen - who he says rip him off.
Poly Network said it hopes the hacker will contribute to the blockchain sector's development upon accepting the $500,000 reward, Reuters reported.
Poly Network's pleas for the money back appear to be working. The hackers said they stole "for fun :)"
The surge in interest in ether and the ethereum blockchain was clear to see in Coinbase's Q2 earnings.
The hacker appeared to be returning part of their loot to Poly Network after saying they would do so if the DeFi platform met certain conditions.