This was to be the eleventh episode of the season, but it was aired earlier to game the sweeps ratings with stronger episodes.
Matthew Abaddon is Locke's driver. The Hebrew term Abaddon appear in the Bible as both a place of destruction and an angel of the abyss.
Charles Widmore gives Locke a phone and tells him to ring 23 if he ever needs to get in touch - one of the hatch numbers.