The certificates will have value as long as they remain evidence of honest completion of the course. To say they are worthless is kind of short-sighted. Considering the number of tech resumes in the typical hiring manager's inbox that contain a laundry-list of programming languages in the skills section and not even a single project or course to prove the knowledge of the candidate, I'd say there is a fairly large domain for these certificates.
Given two resumes, one with a big bullet list of unverified skills, and one with a bullet list of some completed coursera courses, which would you choose?
Obviously coursera will not be replacing real college any time soon, but it can definitely serve a role in verifying at least cursory knowledge of basic skills.