Unvested stocks are not your wealth. Try not to think of them that way. You own them the same way you own next year's paychecks, i.e. not at all.
There are ways to mitigate this risk. Talk to a professional.
As long as you heed standard advice (treat stock as nice to have but value it at zero during wage negotiations) then the impact on your net worth should be minimal :)
Oh man, so sorry.
Not really, if they go to zero, then he/she will be in the same situation as most (99.9%) of employees who get no stock.
We call it the lottery — the last ~5 years we "won"; this year? Maybe not so much.