How much the honey pot practice is efficently against spam?

[Arkk]

With honeypot, i mean more or less this practice:\[code\]#Register form<style> .hideme{ display:none; visibility: hidden; }</style><form action="register.php"> Your email: <input type="text" name="u-email" /> Choose a password: <input type="text" name="passwd" /> <div class="hideme"> Please, leave this field blank: <input type="text" name="email" /> #the comment is for text-browser users </div> <input type="submit" value="http://stackoverflow.com/questions/3622433/Register" autocomplete=off /></form>//register.php<?phpif($_POST['email'] != ''){ die("You spammer!");}//otherwise, do the form validation and go on.?>\[/code\]more info here.Obviously the real fields are named with random hashes, and the honeypot field can have different names (email, user, website, homepage, etc..) that a spambot usually fillup.I love this tecnique becose doesnt not cause the user to be annoied by capthcaWell, does anyone of you have some experience with this tecnique?How much is it efficent?