Crowdfunding sites like SoMoLend aim to act as a kind of financial launching pad. “Crowdfunding can get companies started to the point where they can get bank financing down the road,” says Mr. Scearce of Emery Credit Union. “We’re excited about what this can do for the economy — it can get a lot of companies up and running. And we’re excited to be in on the ground floor.”

In October, Ms. Klein formed a partnership with Gate Global Impact, a broker-dealer based in New York, that allows SoMoLend to add accredited investors, as well as family members and friends, to its mix of lenders. That paves the way for what she calls “leveraged loans,” so that institutional lenders can feel more confident knowing that a borrower who has raised money from friends and family has some “skin in the game.” It also moves her closer to her goal of enabling ordinary investors to “invest in the products, people and companies that they already know and love.”

HER hope is shared by dozens of other start-ups that geared up after President Obama signed the JOBS Act. One of the law’s crucial provisions allows private companies to sell shares to the public over the Internet, but it stipulates that such investments take place on a new type of Web site known as a “funding portal.” The S.E.C. was given until the end of 2012 to flesh out the legislation with detailed rules.

Thus, last spring, the race to reinvent finance for the Internet age was on. With their eye on early 2013, dozens of ambitious start-ups began preparing their crowdfunding portals. They watched the stunning success of sites like Kickstarter and Indiegogo, which have helped raise hundreds of millions of dollars in donations, and they vowed to do the same for entrepreneurs. (Donation- and rewards-based crowdfunding is not covered by securities laws, which kick in only when a financial return is promised.)

Those dreams have been stalled, if not exactly extinguished. The S.E.C., sensitive to critics of the new law, has missed its year-end deadline. Turnover at the top of the agency — Mary L. Schapiro left as chairwoman in December, and a permanent replacement has not been named — could further slow progress.

Kevin Callahan, a spokesman for the S.E.C., wrote in an e-mail that the agency had been working very hard on crowdfunding rules and had said both before and after the JOBS Act was enacted that the year-end deadline was unrealistic for such a complex issue.