It will be interesting to see if this works. del.icio.us is a good demonstration of sharing and storing links with attached context but very few users use this aspect of it. I sense that many users do not have enough time or inclination for such advanced features.
Lightweight linksharing. Friendfeed, twitter, tumblogging, and now google enters the space.
I think this is probably too tied to gReader to make a real go of it... but this particular problem is ripe enough that I'm working on an idea in the space, too.
It's a nice feature but I doubt it'll get used much. For sharing to happen you need to first create a space where people enjoy hanging out with their friends, and that's not really what Google Reader is.
The share button is so trivial to click and the sharing is forceful (i.e. it appears in my feed without me ever adding the friends or letting them share stuff with me implicitly) that I think it will actually be used a lot.
