A brief and unscientific survey of social bookmarking buttons provided by journal websites. Take with pinch of salt and/or tongue in cheek.
I know, all bookmarking services provide their own tools, such as bookmarklets. However, I suspect that a button is more convenient for many people: it’s a courtesy and an advertisement for social bookmarking and online reference management tools.
So NPG: is it “we promote sharing” or “we promote sharing so long as you use our service?”