It is not really necessary to perform the programming yourself since there are a lot of free tools/components that you can use.
Some of my favorites are:
- Free Captcha - but not sure how it will impact the performance since it needs to talk to the provider.
Other things to be aware of captcha are:
- There are now more sophisticated tools to defeat the captchas.
- More and more users are getting upset and turn off by captchas so it may cause you to lose your main customers.