After parsing the comments, I have not seen one person mention management or leadership. Someone with 20 years experience hiring and leading teams is going to be much better than someone doing it for the first time in their life. The ability to know your weaknesses, surround yourself with good people who fit your vision/culture and address those weaknesses, is not something most 25 year olds can do. Most at 25 have no idea what their weaknesses are. which makes it all the more impressive when people like Zuck, Spiegel can scale into massive companies.
But I also understand why you would want to invest in a 20-something. On average, they are going to be more aware of emerging tech, and guided with the right advisors can get a company off the ground and then supported with the necessary pieces.