The consensus seems to be that book icons are fine when talking about one’s books, and can be used indefinitely there–but are probably a little problematic when always used for talking about everything. And that what one’s default icon is matters much less than how one uses one’s icons, which makes a lot of sense.
And also that really, it just doesn’t matter all that much–not nearly as much as, say, what a blog is actually saying. 🙂