You may be surprised to hear this, but even I, author of a blog that never updates, become increasingly irritated at other blogs that don't have new posts. Eventually I will just remove them from my favorites.
Drew of toothpaste for dinner has an excellent blog post about this phenomenon. It also explains, right away, why my mom does not have a blog. Something about arm dogs.
One of the best things about Note of the Living Deb (which I always misremember as "Site of the Living Deb") is that she posts every single day (except during the occasional vacation or something, but usually even then). Way to go, Deb! It's really nice not pointlessly checking someone's blog all the time.