Almost every developer at some point will be approached by someone to work for free for some killer idea that that person had. In those cases, I found it useful to have them fill out a checklist list this, or put together a multi-page Executive Summary and a Business Plan. You'd be surprised how quickly you can get someone off your back and them off their idea, if they now have to go and do some actual work. And you never have to say 'no' and get that person offended.
This checklist is actually pretty good. But I usually ask them to put together 30-50 page Business Plan with an Executive Summary. If they don't know how I tell them to look online for examples. In one case I pointed them at a local startup incubator that runs workshops for things like this. All this does is add up to a non-trivial (but not onerous and with little cash outlay) investment of THEIR time. And if this small investment of their time is too much work for them ... well, I guess they weren't that serious to begin with.
So far I'm 5 for 5 when asked for a 50/50 partnership (where I do all the dev work and my partner is the 'idea man') and then never hearing again about the idea after I asked they put together this document - all without having to say 'no'. There has not been bitterness on their part, because next steps are on them.
In the off-chance they will actually do this (and it hasn't happened yet), I will take it seriously and really consider it. But even if I decide not to pursue it, I feel like the exercise isn't a waste of their time as they will be able to use it when looking for funding or other partners.
As someone in your spot (solicited by ~10 or so people in the past couple years), this is an interesting response.
On first blush, it seems to set an adversarial tone rather than a collaborative one. On the other hand, it's good due diligence and probably filters out the serious from the not so serious.
I mostly agree with your response. I think the only place where it may not work is when the person wants a thought partner to help think through these things. There isn't always a strict dichotomy of duties in the framing of a venture - I think all partners should be involved in that. Different story when it comes to execution, though.
