Thanks for posting your ideas and techniques for using Reverse Captcha.
I pretty much agree with all you've said. However, it's hard to get actual data on the effectiveness of Reverse Captcha and Captcha techniques, so many conclusions are "gut feel" or guesswork.
Certainly, all forms we've used that have Reverse Captcha on our site, and customers' sites, have been effective in stopping random spam.
This is a good idea, and avoids the problems you suggested for accessibility.
I am considering adding a visible honeypot field named Site URL or something, with the label “Spammers: Enter your website’s address here. Non-Spammers: Leave blank or else…” or some such.
However, I don't think you want to use the word "spam" or "spammer" anywhere. A message such as this should be sufficient:
Where "revcap" is a CSS class that does "display:none".
<p>If you can see these fields, please ignore them. We've included them to help protect the internet.</p>
Address: <input type="text" ...>
Blah: <input type="text" ...>
It's useful to groups spammers into two classes:
If your site is *really important* (such as Google, Microsoft, etc.), then you will be hit by type #2, and there's not much you can do to stop it (but you also have plenty of money to deal with it too!) The spammers can write special software, they can fool people or pay people to fill in forms for them, etc.
- Random spammers - they and their bots look for any form on any site and try to utilize it.
- Targeting spammers - they attack a specific site.
Most of us only have to deal with type #1. FormMail's automatic anti-spam features are sufficient to deal with most of these attacks.
Reverse Captcha will take out another chunk of these attacks, and in most cases stop it all.
One last thing...
If you think Captcha provides some "kudos" for your site, then you can always implement Catpcha that does nothing. So, the form looks like it has Captcha, but user mistakes are ignored.