App Store now provides an easy way to report scam or other problems with apps. Rollout is gradual, more and more users will see this button soon.
Easy way to report scam might also trigger more reports on legitimate apps. Therefore, there might be more reports and refunds on existing apps. As of now button is not available in all countries.
UPDATE: Apple confirmed that 'Report a problem' button is introduced to fight scam on App Store. Web version of the tool is also available.