The first question to answer is if the site itself is a blog... or if it's a website that also has a blog. If it's the latter and the blog lives at www.yoursite.com/blog/, then the structure should obviously always include the /blog/.
Responding to your 3 examples in order:
Quicksprout's structure is a little odd in that their blog lives at /blog/, but the individual posts do not. A bit strange from both a human usability and bot crawling hierarchy standpoint. Other than that, including the date is helpful in terms of telling the user/bots how current the post is and differentiating it from similarly named posts on the same blog. That said, it pushes the title/topic keywords further out in the URL.
Moz uses /blog/, which again makes the most sense, but they've foregone including the date. This, however, lets them get the topic/title keywords to appear earlier in the URL.
SEO Book, like Quicksprout, oddly strips out the /blog/ directory from the URL. Other than that, their strategy is the same as Moz.
The winner here, in our opinion, seems to be Moz. The /blog/ remains when you're on individual posts which makes sense to both humans and bots. They don't include the date, but historically that's not been critical.
