Gervase, I will agree with you completely. As far as I can tell from the Ubuntu side, we really only gained one contributor, the excellent Manu Cornet. We also had similar issues with people not being part of the community and thus not really joining it during or after. However, I would add the following suggestions:

1. Code should be developed in a public source repository
2. Projects should post a clear page with who is working on what, and what the status is
3. SoCer's should post status reports regularly (ie, more than just once or twice)

I should note that I was not involved with the planning or execution of any of the Google SoC stuff here at Ubuntu, this is merely an outsiders view. I should also note that Google is not really at fault here. One of the problems that I think Ubuntu ran into was simply that all the development team was too busy to effectively tutor the SoC people. Again, that is just an outsiders view. I could be completely wrong.

However, I don't think there is anything systemic wrong with Google SoC that is not fixable this time around.