Recaptcha isnt the best way to protect your site
Against spam, the best way I've seen so far is thusly.
A HTML form, has many inputs, a computer sees them and just inputs something in order to get the form to submit, but since it doesnt know what information is needed or not, it fills in all the fields.
So basically, you have to separate the computer and human apart, based on what they fill in. Recaptchas and the like are slow, ignored, awful, breakable and basically turn people away from sending in vital information your site could need.
What if you build a HTML form, with a section of it, which was position absolute and visibility hidden style attributes on the page, they are <input type=text> fields and basically, the idea is, you dont fill them in.
Because the stylesheet is being used to obscure them, without a stylesheet, they would be visible, or maybe, with no comprehension of a stylesheet, they would be visible also.
SO basically, along comes the human, with his web browser, fills in the fields he can see, sends away, all the ignore fields are empty, obviously a human, a computer comes along, sees the hidden fields, has no ability to read the css or know they are supposed to be hidden and then fills in the ignore fields, therefore tripping your validation into knowing they are a computer.
It's simple, but I think it's FAR more effective than captchas.
Anyone find a flaw in that plan? sounds perfect so far.