When someone creates a product specifically for a certain group of users (in this case folks installing extensions) without actually knowing what is useful to them (never even mind 'important' at this stage), there is something seriously wrong with that process.
Though I might only be a single voice, I just want to say that as someone who installs extensions, I support this project. While its generally pretty easy to tell that an extension is abandoned, it isn't always easy to tell if it is any good.
I would consider a rating system for extensions a perfectly viable GSoC project that has both useful and important implications.
Thank you, Derric Atzrott