I think that the Captchas on the Programmers Blog are a bit too difficult to do. This may be a good thing if you are trying to prevent comments (sarcasm, did not think I needed to say it but question was edited to mean the opposite), cannot understand the words on many of them. Plus, the form is not re-entrant (meaning if you get the captcha wrong you lose what you wrote unless you go back in browser - and in the future someone does not add the header to not cache or whatever browsers want to not keep the previous page(s).
Can we fix this? A good captcha would be some of the new ones I have seen that ask you a question and you need to choose one of four, or even a home grown one with varying font style and sizes, plus random noise (lines, dots ...)