I use a CAcert SSL Certificate for the following reasons:
1) It’s Free, as in both “Freedom” and “Free Beer”. Using a CAcert costs only the time it takes to get assured and the time of those who have verified my identity. I don’t have to pay CAcert to use their services, saving me hundreds of dollars. However, I do volunteer my time back to the CAcert community as an assurer and I am more than willing to assure you if you’re interested in creating your own CAcert certificates. You should also consider donating to CACert.
2) It’s more secure than just buying a certificate. I could buy an SSL Certificate for a few hundred dollars from a Certificate Authority (CA) with just a credit card. Even if I did use a credit card in my own name, odds are pretty good that a randomly chosen CA is likely doing business with the NSA. Before I could get a CAcert SSL certificate, several real human beings had to verify my identity. Furthermore, thanks to diligence by the community, I believe it is far less likely that the CAcert root certificate has been compromised.
3) It’s a community effort. When given the chance, you should always support a viable community effort over a rent-seeking industry.
Please feel free to ask me any questions on this, or reach out to me to assure you.