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Bob would read through his news items using this interface. He would scroll up/down to look at the news itemsby scrolling up and down. The first few lines of each item are visible.

The political article would be long enough to be cut off, but he could read all of it inline by expanding the article with the disclosure triangle. He

Since articles are automatically marked as read as he scrolls through them, When Bob is interrupted, he would hit the 'save later' when he decided to read it later, which would cause it to show up in this stream again some time in the future.
He would share the imgur image by pressing its 'share' button, and press 'tag' to put it in the 'cool' category. The tag button would be come 'add/edit tags' after there are tags assigned.
Items would be marked as read automatically as he scrolls past them.  to indicate that the item should show up again the next time.

This interface is very similar to ones people already use to view information (Twitter, Facebook, reddit, etc.). In addition, the vertical list format is very common on phones, so Bob will have little trouble learning how to go through his news items.  the interfaces for reading Twitter updates and Facebook's stream. The list format (common on phones) affords scrolling through the items, and the buttons use text to be fairly self-describing. Bob should have little difficulty figuring this UI out.

It is very efficient for reading items. Bob can quickly scroll through and skim the first line of each entry as he looks for things to read. However, If he wants to mark multiple items at once (such as read or read later), it will not be easy or quick to do here because he has to do them all individually. Having the buttons always visible may mean more scrolling is necessary, which could slow Bob down.

Bob can easily expand/shrink entries. With this interface, items are currently not deletable, which avoids Bob accidentally removing something he wants to keep. If Bob doesn't like a tag he put on an entry, he can edit or remove it using the "tag" button again.