The first 1000 people at Facebook are millionaires. http://www.washingtonpost.com/business/technology/facebook-1...
Any early Facebook employee has both the money and the name brand to be a credible founder.
By contrast, have you founded a successful startup? Have you raised money from investors? If not, why would you feel qualified to offer advice on the matter?
Just being "early" at Facebook isn't enough to create credibility. A person also needs a track record of promotions. Millionaire or not, no one's going to fund someone who joined Facebook in 2007 and didn't get promoted in the interim.
Startups are a lot worse than people assume when it comes to internal promotion. The selling point of a position at a startup is the ability to get in early and have promotions be "inevitable" with growth, but it's equally common that as the company needs to scale, it has to bring on more established people, and those people tend to want leadership roles if they are going to join.
It does sometimes happen that someone joins a startup out of college and is a VP within five years, but that's not the norm. Just as common is for a person to end up a "paper millionaire" but languish in vesting twilight, not getting the raises and promotions that would be available in a more stable company with a better sense of career development.
Of course, there are a lot of great startups out there, where a person can learn a lot very quickly, but those are not all of them and joining a company because "it's a startup!" is, without more knowledge, a bad idea.
That's the bubble I see: people taking jobs in dodgy startups for ridiculously low equity slices based on information that's either biased or only validated by the ridiculous echo chamber, thinking that their position as Employee #57 is going to make them real founder material in 8 months (because the CEO will just give them investor contact). It don't work that way.