If you've been following the PRISM/Edward Snowdon revelations, you'll be aware of how insecure online communications can be.
If you're a journalist, you more than likely have sources you need to protect, and confidential information you gather. No online communication can ever be truly safe, but you can go a long way towards it by encrypting your e-mail.
I've just set myself up for this, using the simple instructions for encrypting your e-mail from iMore.
If you're serious about journalism - do this.