How much does participation in online predictive challenges (DREAM, Kaggle, Innocentive) improve your resume? I'm getting curious about all these online predictive challenges going on, such as DREAM, Kaggle and Innocentive.
Surely they all are good occasions to work on new projects and new ideas, to know other collaborators, to get important training about science, and to possibly win some money

And also they could represent a good point in one's resume. So I was wondering: in job application processes (in both industry and academia), do candidate selectors care about the participation of the candidate in any of these challenges?

If yes, how much?

If no, why not?
At the very least, it shows you are actively interested in the subject.  Participation can be enough to show you are more enthusiastic about the subject than other applicants.  It is also helpful for entry level data scientist positions where experience isn't necessarily expected, but appreciated. If you have won any competitions, or if you are at the 'Master' Kaggle level, definitely include it.