From MozillaZine Knowledge Base

Deleting files is not safe!

So why do we always give that advice?

We just had a user who came to this article after losing bookmarks. Under what circumstances should we recommend deleting a file as a remedy for missing information?!! Consider that that file might be the only copy of the data. I can't think of any circumstance in which this is necessary, or even a good idea. Is there something I haven't thought of?

Remember, we're dealing with confused users. I wish we would always tell people to rename files, not delete them.