What?
Unless your work literally drives you to suicide, the cap on the downside is 'You go out and interview until you find another job.'
You aren't risking your own money - you're an employee. You get paid for your work.
If want to work on your idea, but you don't already have connections to tap for immediate VC funding, any work you do on it is earning $0 income while you're still having to pay the bills. Your downside risk is that after X number of months or years, you've lost $Y dollars of your starting savings.
If you take the Microsoft offer, your downside risk is that after X number of months or years, you get laid off, and have to look for a new job, but your $50k is still there, and quite possibly a bunch of new savings as well.