I've experienced a problem with the reader updating posterous.com blogs - joshlore.posterous.com is the blog I first noticed it with. You have to manually update the feed, and then it doesn't display the page in story view.
I'm still getting the same problem. The fact that it's not showing up in Story Views isn't a big deal to me, but the fact that it's not auto-updating, that I have to right click and manually updates, to recognize new posts, is a concern. I've tried it out on a couple different computers, with a couple different accounts, just to make sure it's not a local thing, and it doesn't seem to be.
So Posterous is preventing embedding in an iframe, which is why the Story view doesn't work. However, I just subscribed to joshlore.posterous.com and will see if it continues to update. Next time you post, let me know if it doesn't show up on NewsBlur.