For me the lack of working product would be the first and only sign of a fraud project. Such times have passed when a project could scam people with a good whitepaper and original website. Investors are getting smarter.
as I know project trying to gather the funds using ICO is to realize or make an execution to their idea and thus resulting in a working product, maybe some of the projects out there are already having a working product even before the ICO being announced but it's still not right to judge a project as a fraud just because of not having a working product while the sole purpose of creating an ICO is to gather fund.
Maybe it's better to judge them by whether they are following their roadmap or not, although there are some other factors aswell.