piatkow - 12:02 pm on Jul 19, 2013 (gmt 0)
As the bots typically fill all fields I did once consider having a field with the label "do not enter anything in this field" but considering typical user behaviour I thought that wasn't a good idea.
I have two forms on one of my sites. One dates back to my early days with "free" hosting that didn't support PHP and uses a third party service, the other uses a PHP script on my server. The third party service doesn't let through any spam but my own script gets one or two a week. The spamers' scripts generally drop the same text into multiple fields so I have filters to catch the most regular combinations. Its not enough to warrent inconveniencing customers with a captcha.