If you haven't made any policy changes, user changes, license changes ... things of that nature, then you're really safe with once a day. You'll lose some statistical information, but you won't lose functionality.

If you decide to create a software configuration and assign / deploy it to users and then your DB crashes and you have no backup since you've created / set for deployment then you'll have to reconfigure.

I generally do hourly backups only because the impact is nil to the SQL server ... but daily is certainly ok. Its better than nothing at all, which unfortunately is what most MSDE installations end up being.