All of the questions about tester certification were answered many years ago. They exist and they cannot be made to unexist. The only remaining question on the subject is: how many tester certifications can be sold? And the answer to that question doesn't matter to anybody except the people selling the certifications.
A while ago on the writing-about-testing mail list we did a little exercise to come up with some back-of-the-napkin estimates about the number of software testers in the world. We used US Department of Labor data and also some other public information about software employment worldwide. We also had access to some privileged information about magazine subscriptions. In addition, a number of us have done serious work in social networking, and we have some analytical tools from that work to help estimate. Using all of that, we came up with a pretty consistent estimate that there are probably around 300,000 software testers in the US, and maybe 3 million in the whole world.
That is a pretty small market in which to sell tester certifications.
Elisabeth Hendrickson recently did a fascinating analysis of QA/testing job ads. According to her data, it is a good bet that 80% of the people doing modern software testing work in the US have programming skills of one sort or another.
Jason Huggins of Sauce Labs has been tracking job ads that mention browser automation tools. Jason notes a remarkable recent increase in the demand for Selenium skill. You can see the trend for some popular automation tools at indeed.com. The QTP vs. Selenium trend in job ads is fascinating, but looking closely, this graph indicates a general across-the-board increase in demand for technical skills in traditional UI-based software testing.
Finally, sorry I don't have a link handy, but I have seen a number of reports of a radical increase in the rate of adoption of agile practices among US companies of every size and description. And the agile whole-team approach to software development makes dedicated, siloed traditional V&V test departments irrelevant.
The existing tester certifications simply do not apply to this sort of work. Certification is becoming more and more useless to US testers, and to their employers as well.
I feel like I am pretty plugged in to the world-wide tester community and the world-wide agile community, and anecdotal evidence suggests that indeed, the market for tester certification in the US is very small. Again, this is anecdotal evidence, but the hot spots for certification seem to be the UK and Australia/New Zealand, possibly areas of Southeast Asia, possibly areas of Eastern Europe. Once more with the anecdotal evidence, but I would suggest that in political climates that favor a high degree of regulation of business practices, certification will be more popular.
So if we eliminate from our worldwide tester population of 3 million the majority of US testers and a significant fraction of the rest of the world as potential buyers of a tester certification, that leaves a pretty tiny market for tester certification.
I think we can say with some confidence that professional tester certification can safely be ignored by the vast majority of software testers. That said, if you are required to get a certification, or if you just want to get a certification, go ahead and do it. It won't hurt you, and at the very least, you'll learn how software was tested in 1996.
I think we can also safely say that any supposed controversy surrounding tester certification is overblown and can also be ignored.
Which suggests one more interesting question: if the supposed controversy over certification really is as trivial as these statistics indicate, then why does so much of the testosphere spend so much time agonizing over it?
I have a cynical answer to that, but I'll keep it to myself.
Update: made the links nice