Adding honeypots is simple, just add some field, hide them and then check on there values after submitting.
But this plugin makes it simple and DRY.
Install
script/plugin install git://github.com/grosser/honeypot.git
Usage
Controller:
before_filter :check_honeypots, :only => [:create]
OR - if the default render new + flash[:error] is not what you want
def create
render :action=>'error' and return unless honeypot_untouched?
...
end
Forms:
=honeypot
Michael Grosser, the Blog 
Can You comment more about this plugin.
Lets say why You have created.
To prevent bots from signing up as users in our app, which created lots of false users