We didn't open source because we're a bunch of freedom-loving hippies (OK, that was part of the reason) we did it because it made sense.
There would be no reddit if it weren't for open source software.
It wasn't compromising the success of the site because the real value of reddit is in the community.
Contrary to doing damage, we actually increased our credibility as a democratic social news website; to date, reddit is still the only big player with total transparency, which is a bit ironic given all the hand-waving about "taking power from the smoke-filled back rooms of editors and putting it in the hands of readers."
Thanks to a savvy userbase, it meant our code would benefit from a variety of unforeseeable improvements from bug reports (and patches!) to new features and add-ons.
In fact, there might be a good reason or two in there that also applies to your business -- even if you're not a community-driven-social-news-website with an alien mascot.
Open source your business practices
Remember that blog every social media guru was telling you to start a few years ago? Now it's Twitter. But these T.W.A.T.s (Total Web Attitude Trackers, as they're more recently being called) are right about one thing: creating content is easier than you think. And chances are, you're an expert at something in your field. And unlike at cocktail parties, on the Internet, the more esoteric your skills, the better! (To a point: I'm looking at you, Amish-style miniature butter churner artisan).
Why not share tips that your peers in your industry can use? Don't wait for Harvard to write a case study about you. It's not just for the karma, it's to build your brand as an authority.
Dharmesh Shah has done this with great success for the startup community and the 37Signals blog is a go-to resource for designers & software companies, but these are the kinds of industry where you'd expect it.
Expertise in a niche industry just means more credibility
We at breadpig (my night-gig) have tried to do that with the random merchandise we've created, like our guide for making your own custom magnetic poetry. What's the cost? Just some time. There's already a competing brand to our LOLmagnetz that copied the idea, so why not show everyone exactly how to take the idea from inception to final product?
Chances are, you're going to gain a lot more by sharing various industry tips and insights you've acquired than you'd ever loose. So start sharing on your blog, through your twitter, or even write an eBook. Just get your ideas and knowledge out there, because chances are, they're a lot less valuable than you think -- execution is what matters.