MyStickies, Sticky Notes for the Web

So in the context of informal education, or education with pre-defined cohorts, open annotation tools like these ones make some sense (though potentially the amount of cruft you'd end up seeing could make them unusable, as is the potential for 'annotation spam' ick) but it would be interesting to see annotation tools like this integrate with people's instant messaging buddy lists so that you could leave messages attached to web pages that could then be filtered by whether you were on somebody's buddy list.