[tsm]

I find an exchange like the following hard to imagine:

Technical Cofounder: We can't realistically do <foo> because it'd have to process a huge amount of data and it'd take way too long.

Ignorant Non-technical Cofounder: I don't believe you! You're just a dumb programmer.

Enlightened Non-technical Cofounder: Oh, you're right. I can see that it's O(n^2).

My advice, for what it's worth, is to find a technical cofounder you trust, and then give him the benefit of the doubt on any features he says are unimplementable.