How crucial is the fit between partners in a start-up? Have you investigated this aspect of formulating the start-up package? Have spoken with experienced investor and entrepreneurs? Would you use an online questionnaires or guides to evaluate potential candidates and close gaps between candidate's perception before making a commitment to bring someone on board?
The fit between the partners is everything. It is crucial, because a startup cannot succeed without it.
Would I use such a tool if I believed that it is accurate, yes. Is it likely that I will believe in the accuracy of such a website? No. Would I pay for such a service? Probably not. Do I believe that many other entrepreneurs would use such a tool, I am not sure.
Many people start a company with their friends, and an online tool will not convince them that they shouldn't do that.
Finding the correct partners is a problem, though I am not sure that a questionnaire is the solution
How crucial is the fit between partners in a marriage? :) It's the same thing, but with a lot more on the table. You should use all the care and diligence you would use in finding a spouse in creating a partnership or business. You need to be on the same page in all aspects, including:
Keep in mind you will be spending lots of time with this person and you'd better trust them, like them, and believe that they have your back as much as you have theirs.
Otherwise, you might as well just run everything yourself.