Better question here - who are you to judge this? A prospective employee is by no means forced to accept employment with a start-up where they're receiving a smaller share of equity than the founders. There is no grounds for any sort of argument of what is "fair" when you are on the receiving end of a job offer. If it's not fair, don't sign on. If you don't like the terms of the deal, renegotiate or find another one. The founders / current employees can offer whatever they would like - you have the ability to decide whether or not you want to accept those terms.

Problem with this thinking is that it assumes the employee knows what's fair and isn't being lied to by the startup.

That's really not the case.

my general rule of thumb is: founder is someone who starts before salaries, employee is someone who is paid a near-market salary on day 1.

the risks of starting before salaries are that you will accumulate a ton of debt (or waste away your savings, or both) for a project that ends up going bust. you will lose many friendships, perhaps even your marriage, because you believe so strongly in an idea that ultimately may or may not work out, and you put 100% of your available time and effort into it.

there's nothing particularly glamorous about that statement i just made. starting a company is hard and it sucks and it usually ends in failure with the founders hating each other.

There is no general answer to this one, but I'd say those 6-12 first months are when the company is most derisked. If you're going to be employee #1 of a 12-months-old startup, it means it still exists (vs all those failed projects), so it is much less risky, and founders are compensated for this risk (don't forget that in most case, their huge share of equity will be worth nothing in a few years!).

Of course once employee #1 joins he usually works as hard as the founders and I understand if he wonders why he got so little equity but those first months are more crucial than appears.

Let's take the example of the company I'm cofounding (tldr.io). When we started 10 months ago it was nothing more than a crazy idea with a very low chance of success (summarizing the web). Fast forward to today. We're still not ready to hire but we're getting close. The crazy idea has become a "there actually is a chance, although small, that it will succeed". I feel that the difference is huge.