Eddy Lucast (5/6/2014)
I'm not a fan of captcha systems. There's just too many of them that no longer work. Confirmation emails are a good idea, they'll weed out the bots but not the user sitting behind a keyboard.. Of all those who have successfully made it to our forums to post spam, all replied to confirmation emails. We've also had a problem with the names used when creating accounts being suggestive and NOT something you'd want displayed in your activity panel. We also decided we didn't want dozens of banned user accounts showing up in the list. Our solution for this has been to change passwords so they can't log in.
If you want SPAMMERS to get a different page than a normal user take a good look at the permission set options for your banned user group.
Nothing will ever completely stop the spammer sitting behind a keyboard. If the spammer is sitting behind a keyboard they can easily make fake emails accounts to confirm from, they will be able to proved the right answers to captcha/math problems/etc., and will be able to bypass IP blocks via proxies and IP spoofing. If you give me any system of protection against real person spamming I can give you at least half a dozen ways to bypass it.
Captcha systems are designed to help stop bots and, in general, they do a good job at them but like any system as bots grow the system needs to grow with them. Adding a confirmation email requirement on top of captcha systems adds another layer of protection as most bots don't confirm emails.
I make the suggestion of the reCaptcha system as it is an ever growing system. The current captcha system is old and give the users no control over distortion and static (the higher the level of both the harder it is for bots), what ever captcha system is used in 2013-3 I would really like to see it based off an adaptive system with user control on distortion and static.