I have a mac mini running Mavericks with iPhoto 9.5.1 running on it. I have created a shared photo stream that is shared with a friend who is using a macbook pro (mavericks and iPhoto 9.5.1). The stream is also feeding to 2 gen 2 iPads and 1 Gen 3 iPad (all running iOS 7). There are about 200 photos shared to that stream. Around 40-50 of those photos don't actually show up in the photo stream (whether viewed on the mini where they were shared or any of the other devices). So when viewing the "info" tab of any of the missing photos, under shared they show to be shared to the accociated photo stream more than a week ago, but when viewed under iCloud within iPhoto, they aren't in the photo stream. I can't unpublish the photos from the info tab and republishing doesn't cause it to feed either.
Mac mini (Late 2012), OS X Mavericks (10.9.2), iPhoto 9.5.1