A personal journal is a personal thing. If I record my thoughts in this for say 4 years straight and suddenly in the 5th year the company goes down, How do I recover my valuable memories? (Personal journals are more precious to me than photos)
Thoughtfully designed.
(You want them as a bunch of plain text files? Well, hopefully you are using a nice email provider who gives you POP or IMAP access, like Gmail. Download them, grep, and Bob's your uncle.)