Yeah, this is the thing that's really bugging me. I don't want to bank on people just inherently wanting to share their story and calling in favors. I've got a couple weeks before I can realistically set out, and that will probably be haunting my thoughts the whole time.
Hopefully, I could offer enough exposure to present an incentive, but this only really works for the less established.
then focus on the less established. there are plenty of really interesting businesses in the 'exchange goods and/or services for money' category that have zero chance (and sometimes less interest) of getting venture capital.
Even those that get seed capital are usually interested in talking with interesting people... and if you do this right you will end up with a lot of contacts, and thus be a very valuable person, even without publicity. There is a lot of value to be had in saying "oh, I talked to this other guy last week who was doing something that would complement your product or service."
I suspect that you'll get better stories from folks who didn't get VC funding. Lots of writers try to get stories from people who are likely to become famous or already are, but the others are likely to have better stories.
Also, many people want their story told, not for biz reasons, but because the think that their life has something useful to show other people.
The guy who wrote "The Soul of the New Machine" says that some of the managers said later that having someone around to chronicle the effort improved the experience. He wasn't sure if they were joking when they said that they were going to try to arrange to have a writer around the next time.
Hopefully, I could offer enough exposure to present an incentive, but this only really works for the less established.