We've just implemented saving to your Kindle device (via email) and had already implemented Dropbox saver. Both are great features if you're selling eBooks or digital products.
The expanded view looks a little busy but I didn't think hiding the buttons would be ideal when the user may want to save to dropbox while also sending to their kindle.
P.S. the example item is LukeW's awesome book, mobile first, which I'm not actually selling of course :-)
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