Version control for user created text content

Problem: I am developing a website where users will create, edit and sell stories (basically text files). I want to implement a user-friendly version control for their texts (more or less like Google Docs). I am not looking for a Wiki, I am rather looking for a VCS solution that can be integrated in a website where version control is only one aspect (for instance, I have my own editors, with web, Desktop and iOS versions).

Design details: In my design I would like to be able to deal with 50k users, each with an average of 4 stories (text files) with 100kb each. Their stories would be automatically committed at least every 30 minutes or so. I am worried about the possible overhead and delays frequent creation and deletion and commit of changes of thousands of stories and hundred of accounts. Another concern I have is vulnerability of the data to corruption. Finally there is also the problem of practicality. For the later it may help to know I am programming my server web interf开发者_如何学JAVAaces mainly in Python 2.7 using Django 1.3. With the above in mind I have the following questions:

1. Supposing I use subversion (which I am familiar with, but never used in such scale). Which of the options below is better?
1. create a separate project for each user;
2. create a separate folder for each user, all in a same huge project;
3. create separate files for each user all in the same folder and project (to avoiding processing thousands of .svn headers).
2. Supposing I do not use subversion. Which other VCS do you recommend (Git? Mercurial? ...) and with what kind of setup (in the molds of question above)? Please, briefly explain why.

Why don't you just use a wiki with strict security settings, so that each user can only see their own wiki pages? A popular wiki project is MediaWiki

If you must go with a VCS, I think you would have much better luck with a distributed VCS like git or mercurial. The repositories are lightweight and you could easily create one per user.