If you created something, but nobody was there, does it exist?

In a world where everyone constantly blogs and posts about their work, and discloses how it works and increasingly open sources it, what do you do if you want to keep it proprietary to avoid competitors benefiting from it? I have been in this exact situation, and by doing so, perceive to be "in the back seat" compared to those who constantly disclose and open source their work even if it is nowhere close in functionality or quality/performance.

I'm interested in hearing from other founders / entrepreneurs who have worked on projects for years, which they have publicly shown, but for which they never open sourced the source code or other intellectual property, and have encountered situations where their work has been ignored or dismissed, simply because they didn't disclose publicly how something works, or because they didn't open source their work.