"Make sure you make regular offline copies, you have no idea when an 'editor' might take exception and delete it."

The Wikipedia software keeps a record of every edit made, so it is a simple matter to revert to any previous version. All material can always be recovered.

Link:
http://en.wikipedia.org/wiki/Help:Reverting

One thing the contributors might want to do is put the page on their "watch list." Every time you log in, you can see what changes have been made since your last visit.

Link:
http://en.wikipedia.org/wiki/Help:Watching_pages

The problem is the editors have a lot of power to lock, change, delete and otherwise kill any posting. Reversion is only any use if they don't get involved.

I wouldn't want to rely on Wikipedia as the sole source. If its valuable, back it up.

Good advice.