I agree there is a very large snarky dick contingent on HN who pollute potentially productive conversations with "What a stupid idea" type of comments. (Unfortunately I think this is a symptom of the human race, not just HN.)
However, there are some exceptionally bright people who hang out here who I would love to just brainstorm with--throw ideas out and see what happens. This site has an above-average level of these people I think.
I would love to see or find a group of people who are just interested in getting together and banging heads together and see what comes out. Even if I have no interest in starting a new courier service or whatever, I find it quite enjoyable to take the lessons and skills that I've learned and apply them in a new problem space. I especially love hearing feedback on those ideas from people who've worked in those spaces.
The most promising ideas are the ones that might sound dumb to someone entrenched in tradition.