Angel Labs, a Silicon Valley-based, 40-employee investor accelerator that starts and helps run angel networks around the world, said it has formed a network of about 35 Iranian angels, including C-level bank executives who are investing in financial technology start-ups as a route to modernize their own infrastructure. It's expecting an influx of interest from angels worldwide to get into the country, though executive director Tugce Ergul said it's still unclear what mechanism U.S. investors might be able to use, if any.
Meanwhile, in Iran, with or without American investment, the boom continues. Thousands of visitors stream into Tehran, where the two business-class hotels are frequently sold out these days, said Razzaghi.
Many think it's a matter of time before the United States lifts its sanctions, too. As individual investors increasingly discover that they are stymied, and big businesses like GE — which in February sent the head of its oil and gas division to Iran to seek ways to work within the sanctions — the pressure may grow, said Alavi.
"After so many years of isolation, there are opportunities in Iran in every sector," said Razzaghi.
—By Elizabeth MacBride, special to CNBC.com