The feds still classify cannabis as an illegal drug, but medical marijuana use is now permitted in about 20 states and the District of Columbia. Recreational use is legal in Washington and Colorado.
A Gallup poll released on Tuesday shows that for the first time a clear majority of Americans (58 percent) say the drug should be legalized.
Investors are watching this momentum. Some of them believe legal pot sales will be the next "big thing" and they hope to strike it rich by getting in on the ground floor.
This "green rush" mentality is custom-made for scammers.
"Anytime something has cachet and people are paying attention to it, there's the chance that people with evil intent will take advantage of that," said Bill Beatty, director of the securities division in the Washington State Department of Financial Institutions.