Practical Intranet Development

You'd think that designing an intranet would be a web professional's heaven. You know exactly what browsers and operating systems your audience are using. You can easily identify users for testing. What could be easier than that? But then, few people ever get to see other companies' intranets. How can you learn from your peers? Everyone and his dog needs to publish content on an intranet - how do you ensure that content stays current and relevant? How do you ensure that the temp who is uploading situations vacant ads doesn't break it all? Is your intranet accessible? Or do you really need an extranet, for clients and suppliers? How about security?