I'm all for CAPTCHA systems. I know it can pose some accessibility issues, but in general, I think it does help control comment spamming in blogs.
Anyway, I haven't enabled CAPTCHAs in my WP-powered writing blog. But, I'm having second thoughts about it, as I know one spam-control system being used with WP now is Spam Karma. I'm not 100% sure about how it all works right now, but from what I see at this time, I'm not really that impressed with it for these reasons:
Shai has been managing and blogging here at ShaiCoggins.com for 17 years. Here, she writes about creativity, productivity, and how to recharge for a better, happier lifestyle. She is the author of Today: Life Journal, Colour Bliss: Kaleidoscopes, and a little known children's book. A serial entrepreneur, Shai also currently runs Vervely.com, a boutique digital media agency offering online content, community, and conversion marketing services. Her blogging experience and digital work have been featured in various media, including being listed in Fast Company's "Most Influential Women in Technology" list. Originally from Manila, Shai lived in Singapore and the USA before moving to Australia with her British husband. They have two children, a pet bunny, and a rambunctious rescue Labrador.