It's possible, but the concurrency issues will be so terrible you won't want to bother trying. The primary issue is that with a text file, the only way you have to update it is to rewrite the entire database. Not only is this potentially long operation, but only one user can do this at a time. But wait--it's even worse: because of the stateless nature of http, there isn't any practical way to lock the database when the user loads the data into a form to edit. So when the update takes place, you overwrite any previous changes.
