The Mumbai police on Thursday asked border check posts to prevent   former billiards champion Michael Ferreira from leaving the country.

Ferreira failed to present himself to be questioned about the alleged Rs 425-crore scam by QNet, in which he has shares.

The firm has been accused of duping investors through a pyramid scheme. It sold products like magnetic disks, crystal balls herbal products and holiday schemes through fraudulent practices, the authorities said.

A pyramid scheme promises rewards to investors for enticing other investors into the company, rather than increasing its profits by selling real goods and services. It's quite popular in India, too. As of March 2013, the government had received complaints about 87 companies that allegedly defrauded investors through pyramid schemes last year.

Here are four other pyramid schemes that Indians have fallen for in recent years.



1) The SpeakAsia scam

Singapore-based SpeakAsia Online limited asked investors to pay Rs 11,000 and fill up online survey forms to earn Rs 52,000 a year. Additional rewards were promised for those who enrolled more people into the scheme. The scammers made away with Rs 2,276 crore from 24 lakh investors.



2) The Saradha Group chit fund scam

The Sarada group was  incorporated in 2006 and named after Sarada Devi, the spiritual consort of the mystic Ramakrishna Paramahansa. It employed various ruses to lure investors, mainly in West Bengal, and evade the Securities and Exchange Board of India's oversight. It quickly built up a wide network by returning almost 40% of the money deposited by the initial band of investors. When it collapsed in April 2013, it caused an estimated loss of Rs 200-300 billion to more than 1.7 million depositors.

Sudipta Sen, erstwhile chairman of Saradha Group, has since been arrested and investigations are underway.



3) Amway scam

William S Pinckney, the chief executive officer of Amway India, was arrested in May 2013 for allegedly involving its distributors in a pyramid scheme. The Amway scam did involve the sale of actual products, but these were grossly overpriced. By luring in distributors with promises of easy money if they engaged more distributors, the company made sure that its overpriced products got passed through an ever-widening net. But distributors eventually lost their money as there was no one willing to take the expensive product off their hands. The money being brought in by new distributors was used to pay off the original distributors.



4) City Limouzines scam

Sayed Mohamed Masood, the mastermind of the scam, told investors across India that their money would buy them a stake in cars like the Toyota Innova. He would rent these out and pay them huge returns. The cars were never bought and the case is now in court. He also promised returns for bringing in new investors, and used this to finance the cheques he paid out to his original investors. He tricked more than 200,000 investors of a whopping Rs1,000 crore.