A very solid list of the intellectual side. The other equally important side is the emotional.
I would at least add: #8 Expected Long-term Passion
I have tons of startup ideas. I think my current list is around 50 and those are just the ones that I write down because they're nagging at me. Just about any of them could be successful to some extent. Most of them would make it over this list.
The thing that would prevent me from work on 98% of them is my own self-awareness. I know that I couldn't sustain my motivation to work on them over the long-term.
Any sufficiently ambitious startup idea is going to be a 3+ year commitment to fully execute on. That means you have to be deeply and genuinely be interested in the problem enough to sustain your for years. That's a very high bar that very few ideas make it over.
I thought about something like #8. It's a legitimate concern for sure. I just tend not to naturally come up with ideas that I wouldn't like working on. I don't feel I can judge very far in advance how much I'll like something 3 years down the line, and most startups are dead or evolved into something else by then anyway.
The idea is very different from the work you'll be doing to implement it. So this #8("Expected Long-term Passion") is a REAL requirement.
For example: you love adventure sports and want to create a marketplace for adventure sprots. The truth is you WILL NOT be doing any adventure sports during the next 3 years. You'll be doing marketing, getting partners to give discounts, sales etc ... On top of that you might have to pivot to doing something only slightly related.
OR for another example: you want to create a nutritional tool that will help people lose weight. You think it will be getting together great nutrtional content and showing it to users is a meaningful way but instead it could involve creating better image recognition of foods.
Also as soon as you take money, your locked into the idea and need to see it through or your never going to work in this town again. Investors hate one thing more than anything else - low effort.
I've just been through all this so I've finally reazlied that "passion" is VERY VERY VERY necessary.
So in addition to all of the above requirements for an idea, it should also satisfy the following :
"If I do this and it fails - I'll still be VERY HAPPY that I spent the last 2 years of my life doing this."
My primary heuristic for finding startup ideas is coming across problems in my own daily life. As long as the problem exists, and I'm passionate about it, the only thing that will change is the solution. That's exactly why it's so dangerous to be passionate about solutions.
There are other ways to come up with ideas, but for me the only thing interesting is solving problems I see with my own eyes. I know there are very good companies built in different ways though.
Check whether you can reinvigorate your passion. What made you stop loving it? Did you get distracted from your original goal? Did you over-complicate it? Did someone else solve it better? Be brutally honest with yourself about what's preventing you from getting excited and fix that.
If you find that you just fundamentally aren't excited about the problem them you owe it to yourself to move on as soon as is practical. Chalk it up as a life lesson and be more careful next time.
I've been there once and I think the matter is very delicate. Sometimes, you have to push through a terrible lack of excitement. Knowing if it's one of those times is hard.
I'll be honest, this is probably the primary fear I have that's kept me from even attempting something in startup-land. Even if I have an idea (EDIT: or discover an existing startup) that I feel passionate about now, I have no idea how I'm going to feel in X months from now. My passions are fickle and manifold.
One test I now use is this: Is the core feature, without any additions, enough to cater to a big market? I've noticed that some of the best startups solve one really important problem and are able to ride that for a long time. Examples include Google, Dropbox, Facebook, and now Stripe.
If no one gets really excited when you show them the most basic version of your idea, then padding it with more features is probably not going to help.
My new favorite that I use now almost immediately is simply, "If I were to give the core product away absolutely free, would people take it? If so, how enthusiastic would they be about getting it?"
It sounds ridiculous, but I have found it brings a quick dose of reality to ideas that I come up with on a whim that are subject to my own bias. For a grossly simple example, if I were to start a restaurant, there is a safe bet that it COULD be successful because anybody would accept food if it were given away for free, especially if it were of high quality. The rest of the process of building a successful restaurant is fairly complicated, but without a product people would be happy to receive for free, there is no business. The level of enthusiasm the people show for the core product is a good indicator of how much they would pay.
Contrast that with a lot of software/internet businesses and that question gets very murky. With a lot of the sites that I start work on I think "if I offered this product for free, would people be excited to get it?" and very often I realize my idea, while perhaps creative, just isn't solving a real need.
An Easter egg for anyone who has been reading my blog for 5+ years. It used to be my example of the dumbest idea around. It was back at a time when "social" was the big buzz and people were trying to apply it to everything, including, apparently, the alarm clock.
It's original incarnation, if I remember correctly, was some software that you ran on a computer in your bedroom (with your speakers on) that allowed your friends to wake you by changing your alarm time. The new incarnation looks just as bad. But they did mix in mobile and Twitter and Facebook!
Ah I see, that's funny. Whats interesting is that I personally know the guy who made that, and worked next to him at Dreamit Ventures years ago (Dreamit's first class) during a whole summer. So you can imagine my surprise to find the link on your site. For the record, very nice guy.
I agree completely though, 'social' was all the rage. Much like 'Big Data' today.
I would at least add: #8 Expected Long-term Passion
I have tons of startup ideas. I think my current list is around 50 and those are just the ones that I write down because they're nagging at me. Just about any of them could be successful to some extent. Most of them would make it over this list.
The thing that would prevent me from work on 98% of them is my own self-awareness. I know that I couldn't sustain my motivation to work on them over the long-term.
Any sufficiently ambitious startup idea is going to be a 3+ year commitment to fully execute on. That means you have to be deeply and genuinely be interested in the problem enough to sustain your for years. That's a very high bar that very few ideas make it over.