I think the a lot the problems people have with Agile Development practices may be attributed to the idea of "bottling" Agile and creating certifications for parts of it.
It's a great way to make good money, but certifying people as Scrum Master is not something I could trust a couple of days at a workshop to do.
Yes - it can teach them a lot, but a good Scrum Master (or just a team lead, in plain speak) is someone who not only knows the "rules" - but someone with experience, knowledge of the team and mostly with an Agile mind.
Frankly, if you have someone with those skills, they don't really need a certification - they can take a "course" and still be just as good.
It feels too much like commercializing the practices of good team management and software practices (much like MSF Certifications - sooner or later you may find that people are going about it all wrong) and that's why people feel that all you're trying to do is make a buck on their backs instead of really trying to help.
I think it needs to keep being a "grassroots" kinda thing, and only then can people still somehow "trust" that this isn't just a buzz.
Just like any certification - managers tend to just on these things and say "ok - all we need to to "certify" 3 people here in the org. to do this, and we're home free". There's a disaster waiting to happen - if people aren't ready to accept this change, or if you send in the wrong people.
Certification does not guarantee anything but a certification. A course is a better description for it - because it only means you learned something - it does not actually mean you can go and do it tomorrow.
There are many talented people I know who have done Scrum Certifications - it does not mean they can't do they're job - I just think they could have done they're job just as well without that "certificate" to begin with.