I spend a lot of time in my new(ish) job at Rattle coming up with ideas, for both clients and 'innovation' competitions and funds like 4iP. It's all pretty stimulating and rewarding stuff (especially when up against deadlines!), but the downside to this is that a lot of ideas you've spent quite a bit of time thinking about don't get commissioned.
We've recently agreed that, rather than consigning these ideas to 'past projects' folder on our shared server, we should talk openly about them and set them free. Maybe something will happen with them, maybe not, but it should at least help demonstrate what we do, and we might get some valuable feedback. We're not even worrying about people 'copying' them. For starters, it's not that unusual for two or more people to come up with similar ideas independently. Ideas are kinda free - it's the quality of the implementation that often counts for more. Plus, we wouldn't be able to produce all of our ideas anyway, even if they were all commissioned, so if someone did go ahead and make something along similar lines to one of our ideas, we'd just be delighted that the idea came to life.
The first idea we've published on the Rattle blog is one that I was largely responsible for, Bands From Here, so I'm hoping it doesn't get too much of a slagging. But honest feedback would be very welcome.
Update: There's some more discussion of this issue over on Ewan Macintosh's post discussing the transparency/opaqueness of 4iP.