With the introduction of a lot of commenting software over the past few months, particularly those that seek out “DoFollow” blogs, I think these lines of defence are essential.

Captcha’s will only normally deter the drive by commenters who you don’t particularly want anyway - if people are keen enough to contribute, a simple captcha does not make it harder to leave their thoughts IMO.

The elegant design solution is to make life easy for real commenters, and preferably computationally hard but at least uneconomic for spammers. I use Akismet, which comes closest to meeting that design goal - it offers no obstacle to real commenters, and stops spammers from using this resource.

There was no single point - there were a group of points, all related to spam, the reasons why there is spam, and the effects that it has on internet marketing.

-Jan

I use Akismet, and it catches up to a thousand spammy submissions every day, of which I habitually check a few dozen a day, to look for new trends in SEO and products being promoted.

IMO, obstacles to user interaction reduce the conversion rate. So Captcha reduces the likelihood of valid user interaction, as well as decreasing spam. I’d rather kill the spam and increase the ease of user interaction. Akismet better satisfies that goal.

Also Captcha should be accessible - and when I looked at Captcha a few years ago, most implementations were not designed for accessible use. Google does have someone looking at accessible Captcha, though.

I know that Matt Cutts’ blog uses a computed response field - but I can imagine natural language parsers that should be able handle the arithmetic, if the blogs this protects become valuable enough.

For cost effectiveness, most current blog spam will be duplicated. Unique comments from unique accounts and unique IP addresses are harder to generate, and way too many blogs have absolutely no protection. The result is that most blog spam is highly redundant. IOW, the evolutionary pressure to evolve more complex responses is currently low - so there’s not much financial pressure to solve written arithmetic problems, and duplication makes tools like Akismet more effective.

I’m less concerned about the impact on my blog and my blog admin, and more concerned about the effect on my clients’ advertising and SEO efforts.

JUST KIDDING! hee hee. Seriously though, I’m wondering why you don’t use a captcha on your comments? Or, perhaps you could do one of those Q & A text fields. Often, they ask something like “What is 8 + 2?”, but you could even ask something about your industry. Perhaps, hmm… something like: “What is the correct spelling of the phrase Mat Cuts?”

-Gradiva