He damn well better, otherwise, what's the point?

This "how much equity" thing comes up ALL the time here. There is no pat answer, but it often seems like every founder/co-founder and first employee has delusions of grandeur about the whole thing.

I'd guarantee that whatever risks you eliminate now are less than 5% of the risks and roadblocks you'll have to knock down in the next year. In otherwords, until you have a product and customer and enough data to make a real extrapolation from, your value is essentially 0.

Alice's risk is exactly the same before or after Bob addresses these theoretical risks.

If Bob wants to haggle over small equity proportions now he probably has his head up his ass.