Janaki Gopalan, Certificates
My Masters in Computer Science came with a specialization in data mining. It gave me all the necessary theoretical background, practical knowledge of using a DM tool and much more than that as it was a thesis option where we contribute to the field.
Spending 3 years in a program obviously gives in-depth knowledge of the domain VERSUS certifcations which are geared towards specific tools. Certifications is not a bad choice, but, If you have the domain knowledge, learning any tool is not difficult.
Nevertheless, in my experience, when it comes to finding a job, companies love to see tool sets in your resume.
Karl Brazier, DM certificates
First I've heard of them. Maybe that is an indication of low interest in them here in UK as opposed to elsewhere? Suspect geographical split of these results could be interesting, as well as of universities that offer these certificates.
Maurizio Sanarico, DM certificates
Certification is often given more value than it really has. There is no substitution for a solid theoretical background, a broad and deep expertise and a thorough thinking about how apply DM and related methods and techniques to subject matter problems (of course with the goal to provide measurable and possibly enduring value).