I found the CSM course very helpful and informative. Maybe the word "certification" puts people off.
Here's a problem: For agile development to stay a "grassroots thing" it has to stay a "marginal thing", too. Alternative methods such as agile and lean development are crossing the chasm, as the saying goes, and becoming more mainstream and more widely used (or attempted, anyway). It can't stay a "marginal thing", and therefore keeping it a "grassroots thing" becomes problematic.
A certain amount of organization and formality is unavoidable if people are to understand what these alternative approaches are all about. That's where the perception of snake oil salesmen becomes a risk. We'll just have to address such questions as they come up.
Certificate can be good for some person in company, which only started scrum. It says that this person at least knows the "rules". It’s better than company with team, which has no experience and doesn’t know the rules, try to apply new methodology just reading some books.