How to stop spam robots without using a captcha

We have been thinking about how to stop the spam bots without using a captcha. Most Captcha’s work to a certain degree, but in general you do not want to make it any more inconvenient for real people get through your web forms. Well Bob nailed it, just add a css class to the form field that says display:none, robots will fill out this field and real people will not.

So kill those super annoying captchas….personally I cannot read half of them anyway.