Google Reader messes up the shared tag feed - includes items shared by those I follow

Something odd his happening with my Google Reader - "MacOSX" shared posts. I'm seeing posts I know I didn't share - including posts I've not yet read!

They are OS X related and they're mostly interesting. So is it due to some corruption with the (increasingly buggy) Byline iPhone app I use? Some mixture of what I share and what those I follow share? Google Reader bugs?

Weird. I'll have to track this ...

Update: I think it's a Google issue. The items showing in the public feed don't match what GR shows in its shared items list.

Update 2: My tag-specific shared item feed obtained from my "manage subscriptions" "folder and tag" list includes not only my shared items, but also items from blogs I follow that have been independently shared by people I follow! This is interesting, but, Google, so very, very wrong. Please don't make me explain why this is wrong, just think about it for a moment.