The white-hot fintech space saw its largest capital raise ever yesterday, with a whopping $1 billion handed to marketplace lender Social Finance, or SoFi, in a Series E round led by SoftBank. SoFi is now valued at over $4 billion.

The money hasn’t (completely) gone to founder and CEO Mike Cagney’s head, however. “I don’t see any reason why we can’t replace” one of the largest U.S. banks, Cagney told the Wall Street Journal. “I say that with all humility.”

The raise gives SoFi a massive runway and puts its long-rumored initial public offering off the table for the time being.

Avant, the marketplace lender, yesterday also came in with huge raise, $325 million on a post-money $2 billion valuation. It seems like investors aren’t spooked by the proliferation of marketplace lenders or the prospect of rising interest rates.

SoFi has facilitated more than $4 billion in loans to date, and CEO Mike Cagney expects to reach $5 billion by yearend. Prosper, which kicked off marketplace lending in the U.S. back in 2006, has loaned over $4 billion in total, and recently bought identity protection service BillGuard for $30 million.

The capital is certainly flowing into marketplace lending unabated, but there clouds on the horizon as well. Lending Club, which has facilitated nearly $12 billion in loans since its launch, recently filed a comment with the Justice Department in responses to questions about marketplace lending compliance. In July, Justice announced that it was officially trying to get a handle on this large and growing market, which has long-expected tighter regulation. The New York Times published a story on Sept. 13 outlining alleged abuses in online lending, in a manner reminiscent of its series on subprime auto finance published last year.

More than 60% of SoFi loans to date have been student loan refinancing, but the new funds will help it move into areas like wealth management and deposits, Cagney told the WSJ.

Matthew Harris of Bain Capital Ventures noted that the raise may signal a strong move into mortgages.

“They are doing high-LTV mortgages in high-priced markets, so their average loan must be $800k-$1mm, over 10x their average student loan,” Harris wrote. “Plus as a new and unproven product, they likely have to have real equity in these loans for the first year or two.”

Emmanuel Marot of LendingRobot speculated the move could be to simply to crowd out smaller players.

“Maybe it’s the ‘Uber strategy,'” he said. “Pour so many resources at the leader in a new industry to virtually block all other companies from entering the market.”

Or maybe the old fears about marketplace lenders will come true, and instead of being a “collection agency for the big banks,” as Ron Shevlin has termed marketplace lenders in the past, SoFi under Cagney’s leadership will seek to take deposits and bite into banking in a meaningful way.

Learn more about fintech at Bank Innovation Israel, Nov 10-11 in Tel Aviv. Click here for details.