If the insiders "know it" as you infer, why aren't they selling everything? Why aren't they selling the marjority of what they own? Diller owns over $1B in stock, yet has sold only 4.5M shares recently, kaufman owns millions of options and still holds the vast majority, etc. Name an executive still employed and you'll find that they are holding the majority of their positions, not selling. What they know is that they have collected valuable companies with outstanding growth potential, although ones that come with a margin of risk as well. Up to you to decide when the stock has gotten ahead of itself in the short term or when the risks of the different subs outweight the growth potentials.