... by hiring the top guy into your company and then cut off all incentives for the community to get interested.
Yes, I'm talking about IronPython and in this case, the company happens to be MS.
Read what Edd Dumbill has to say about it, especially this part:
Third-party patches won't be considered until after the 1.0 release. Hugunin encourages people to be involved, but only in filing good bug reports and feature requests. And when doing this involves a .NET passport, and using the GotDotNet web forums rather than good old mailing lists, it's a bit of a disincentive. Added to that, there's some uncertainty about the freeness of IronPython's license. While it looks free, it's got the same name, "Shared Source", as several Microsoft licenses that definitely are not free.
I have nothing more to say except that such an awesome 'open source' project has been effectively killed off - IronPython may go on to become 1.0 but it is now reduced to a one-man show when so many people could have contributed to it.