+ Free anti spambot service.
+ Super easy to setup.
+ Very effective.
+ No challenge / CAPTCHA pages.
+ Nice integration with Joomla.
+ Free global CDN.
- It requires a DNS change. (But very easy to do)
"Incapsula" solved every spam issue for each of my site without additional costs. There is no need for annoying CAPTCHA's or challenges. It just works and the Incapsula service handles everything automatically.
You will also get very nice statistics of your visitors and blocked spambots.
For the security minded, you are able to activate a
Web Application Firewall with a click of a button. Now this part is in a paid service but it works like a charm. And it is truly the best and easiest solution out there that I have seen. This WAF is able to block hacking attempts in a vulnerable joomla extension before it has been patched by the author. I tested it and it works!