Del.ici.ous/StumbleUpon

The next unit I'm about to start is a media unit - the sudents will need to look at the ways certain events and topics are represented in the media.

I thought it'd be a great unit to introduce a site like Del.ici.ous or StumbleUpon.

Ideally I'd like to create some sort of collaborative list of media sites/stories and am just wondering how people have gone about managing these in their classrooms. I've heard of some having the one username and password which all students share and login with when they want to add something to the list. But I also see having individual usernames and passwords connected as a network would work to.

What are ppls experiences with using these tools in the classroom, what potential issues do I need to consider? What has worked and what really doesn't...