Pyramid schemes are a criminal form of investment fraud in which a large return on a small amount of money is promised, if the initial investor convinces new recruits to invest their own money in turn. The "pyramid" is built on the belief that others will continue to add their own money into the scheme. But once additional investors become scarce, the pyramid collapses and large amounts of money can be lost. Increasingly, pyramid schemes are conducted via the Internet and e-mail.