I use Google Notebook for such purposes, it's free and online and made for taking notes, not storing e-mails.
It's also worth noting that while there are horror stories out there, the majority of them are often the fault of the user doing something horribly wrong (bypassing multiple levels of "are you sure" type prompts) and the number of reports of legitimate problems vs the number of actual users, puts the percentage of problems extremely low (lower than 1% I'd estimate based on my own, non-scientific, research into number of complaints vs predicted user base).
While you're still in the "draft" phase, you can always use IMAP access to get the data offline to your local system, then you have a true backup of what you have online.
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Samuel Butler - "The best liar is he who makes the smallest amount of lying go the longest way."