Does my site concept seem viable?

The idea is great, but I think you will open yourself up to many issues. This is an area that involves lots of legal issues and although the main idea is to connect folks, I would say LinkedIn is what most folks would go to first as it set up already and well known.

And I agree about stealing ideas. How much info would have to be given publicly on your site for an investor to be interested in a business proposition? And even if you hooked folks up, what would you get out of it? Would you ask a membership fee?

Do you have a link to your site?

honestly, i appreciate your enthusiasm but like the others who commented, i think you are opening yourself up to a lot of headaches...

you might look at https://angel.co/   sounds similar

Michael, I think it's a great idea. I'm building a network now that's very similar in a different vertical myself.

I'm going to disagree a bit with some of my fellow commenters here. You'll have to consider your interests and concerns, and get legal advice on strategies to protect yourself, of course.

But even more important for your business model may be for you to consider that your members will have concerns. It may be helpful to empathize with your target market - with the community members you're trying to attract. You'll want to anticipate their concerns and be receptive to them. You could be prepared to show how your network works and how they can interact in your network in a way that addresses their concerns. (Again, I've got similar issues to think through, so I'm thinking this way right now.)

In your case, you are hoping to attract folks who may have intellectual property. Or they may have business ideas that maybe aren't intellectual property but are trade secrets or confidential information that's just as valuable. They may want to see how they legal protections they choose to use (that's between them and their attorneys- not you!) can be implemented in your network. They may have protections like patent protection or copywrite or non-disclosure agreements (NDAs). They may want to know how they can interact in your network while still maintaining the legal protections they've chosen.

Here's just one example of a network mechanism you might offer for them to use. Consider that you could offer them the use of private groups. E.g., they could setup their own groups and invite just the people who have signed NDAs. There they could have their discussions under whatever protections that they've chosen to put in place.

Some may be interested in knowing how secure those private groups are. Or how secure the Ning email notifications are. As creater/sysad you may be asked to consider whether you have to obligate yourself to non-disclosure or even have it in your TOS. You may want to be able to explain any of that to them. And you may want to have in your "How to Use this Network" page some strategies for using the network that allows them to integrate the legal protections they have chosen to use.

And beyond private group discussions, there may be community interactions that would be very beneficial for your members to have right out in the open in front of everybody. These might have value even without any private protected conversations. It could serve as a marketplace in which your members can share the ideas they do want to share. Here they could connect-up with people who may be resources, advisors, partners, or joint-venturers. Then they can go off into a private group and discuss it further under the protection of the NDAs or whatever else they've chosen.

I happen to think the next big expansion of community networks is moving from the mostly social and personal applications we see now toward marketplace-oriented verticals like yours. You'll be pioneering, so you'll have nay-sayers and skeptics. Leave them in your dust! I say go for it. 

Jeff