Reasonableness Standard
  
Was it reasonable for you to take the 87-year-old heiress' inheritance and invest it all in venture capital funds?
She had $8 million to her name; you put $7 million in VC. So let's think about this. Was it reasonable? Was it reasonable, given that the heiress had life expectancy of 89? So she had, like...two years left. And you put her into funds that don't really even begin to pay back cash or stock (like post-IPO or sale) distributions for at least 5 years?
Answer: no. Not at all. It was not even remotely reasonable. Total bonehead move on your end. You'd get sued for misfeasance. And lose.
There is a generic reasonableness standard that's just...out there. Peer review usually determines its dotted line edges and defines "reasonable."