This was quite obvious for a short while after Apple introduced cross-device pasteboards (handoff/continuity) - if your mac had recently copied something into i

This was quite obvious for a short while after Apple introduced cross-device pasteboards (handoff/continuity) - if your mac had recently copied something into its pasteboard, and you opened the facebook app on your iphone, the system would show a "Pasting from mac..." modal progress bar for a second even with no user interaction.