The problem isn't just in startups with stock options; another big place it arises is closely held businesses. You receive the family business as an inheritance and suddenly you need to pay - in cash - 40% of the value of the business. Such a large cash hit can and does destroy many companies.
The solution is of course to require the IRS to allow payment in-kind (shares). Then you could exercise your options and hand over ~20% of your shares to the IRS. Or you could inherit the family business and give the IRS 40% of the the company (which suffers no cash flow hit and continues normal operations). This additionally would prevent the IRS from overvaluing in-kind earnings.
I believe the argument here is that if the government wants to claim that these shares have a certain monetary value for tax purposes, then the government should stand behind that value and allow you to pay taxes with those shares at their claimed monetary value.
The end goal would be to prevent small business (or people with stock options) from going under because the government claims a piece of paper is worth $1m, but in reality it can't be sold at all, or couldn't be sold for such a high value. If the government claims "oh but we would lose 20% of the value in selling these shares" then they are essentially admitting that they overvalued them when taxing you.
[1] http://www.renunciationguide.com/expatriation-and-tax-detail... (Tax on deferred compensation and non-grantor trusts)
Does that really not exist?
For developers at unicorns I think services are somewhat better (e.g. secondmarket, elite crowdfunder).
Not true at all. For the last year for which data is available, 2013, only 20 inheritances of a small business were subject to the estate tax. [See http://www.cbpp.org/research/ten-facts-you-should-know-about...]
Additionally, estate taxes are paid by the deceased's estate. In the US, inheritors do not pay federal tax on their inheritance, and only 8 states tax inheritors.
I have no idea why you and gamblor are obsessing over "mom and pop" or "small business" - that wasn't a claim I made at all.
Companies are giving out time-limited stock buying privilege to employees instead of direct ownership. Additionally, some companies can even revoke the privilege through termination of employment agreements.
If employees were treated as full owners, there wouldn't be a problem.
If the IRS didn't require you to realize gains on the spread when exercising, then a lot of these issues would dissolve. That's not to say folks wouldn't find other ways to restrict employee ownership.