[jamestimmins]

Investors usually don't know better about the tech, but this is exactly how Elizabeth Holmes was exposed. In an interview with Forbes she described Theranos's process as (I'm paraphrasing) "a sequence of chemistries". That sounded fishy to John Carreyrou at the Wall Street Journal, so he started his long term investigation into Theranos, and eventually broke the story.

So the short answer is that no, you can't keep investors in the long run, but it takes time for journalists, watchdog groups, and federal agencies to do thorough investigations.