How to fight the spams in my Q&A site using Question2Answer? The captcha is one option. But the captcha hurts the user experience---it requires the anonymous users input the captcha every time.
The Akismet Plugin for Question2Answer works great for me.
After installing the plugins, you need to set the key for it in the "plugin" management page of Question2Answer. If you have a wordpress.com blog, you can find the key from it.