In this installment of our series on social browsing, we take an in-depth look at Trailfire, a brilliant implementation of collaborative annotation (letting you put sticky notes on other people's web pages). Annotation has been a holy grail for the web for at least 10 years, with past attempts such as Third Voice or even the notorious Microsoft "Smart Tags"; and upcoming products from the top web portals.It's a notoriously hard problem, but Trailfire has n   read more »