I like to say that QTUM turned out to be not a scam. Why? After suffering a very long price decline along with other coins and tokens, the QTUM dev team is still here updating the wallet and the network protocols. I guess Patrick Dai is exonerated from the Bitbay fiasco.
Scam?
The project is already listed Binance, Kraken and Huobide. We can say that the project is in good condition for the general progress. But the stake rewards are a little low for me. There are hundreds of projects on the market that offer much better stake rewards.
Multiple exchange listing does not guarantee a coin is not a fraud. The best indicator for this authenticity is the hard work of the coin's developers. In QTUM case, I am much impressed by their continuing pursuit of refining QTUM's protocols.