Picking up from the original thread...

Bitcoin-related sites that have self-signed or CACert certificates (like mybitcoin.com) look unprofessional and un-trustworthy to clueless non-techies.

I know, I know, a Verisign-certified certificate isn't really any guarantee of security, but that doesn't matter-- if you want ordinary users to start trusting your website, get a certificate that doesn't popup any scary-looking security warnings.