Prior to Access 2007, security of passwords (database and at workgroup user level) has been a joke. Fortunately for us developers, Access 2007 is a big step in the right direction. Even more so if you follow my guide here to tighten up your encryption settings even further.
It's true that the 'one password for all' scenario isn't perfect for everyone, but it's all we've got now that ULS doesn't exist in A2007 format files. In some situations it's just fine, and most of all it's pretty darn secure as long as you use a strong password and follow my guide.
Garry has now written a covering article on the topic here