A project been Popular doesn't mean a project is scam free, scammers can go extra miles just to make their projects look legit. Scam doesn't only mean when a project vanish after raising money through ICO. Some projects develop and launch then forget about the project and it dies down slowly, that too can be called a scam while others their smartcontract get exploited and huge some of money are stolen that destroy the project. When the project developers abandon such project it can also be said to be a scam.
We have had Ponzi scheme scam in the industry that was very popular and many lost money. Most of the popular stalking projects with tokens can also become a scam as scam doesn't have any boundaries. It can be found both in popular project and those yet to be known although majority are in the less popular ones as they can easily scam without getting the media attention.