Destiny down: Why has Bungie taken space shooter offline on Xbox and PlayStation?

Destiny is down for Bungie maintenance

DESTINY is going offline today on Xbox and PlayStation platforms.

UPDATE FROM BUNGIE: "Maintenance is complete. Destiny servers are back online. Thank you for your patience. Game on!"

Bungie confirmed that their space shooter was set for downtime today to make way for scheduled maintenance.
Destiny players have been warned that the offline period is set to begin at 4pm BST, and could last up to four hours.
Bungie say players signed in shortly before the game goes offline will receive prior notice via in-game messaging, while the game will stay inaccessible until the planned maintenance is complete.
The downtime is scheduled to conclude around 8pm BST.
Bungie.net sign-in and Companion app services may also see restrictions during this time, although it is unclear to what varying degree they will affected.
Players may also experience the Loganberry Error Code(s) during this time, indicating that Destiny is undergoing maintenance.
A message from Bungie confirms: "Thursday August 6th, Destiny will be offline for maintenance starting at 8 AM PDT. Expected completion 12 PM PDT."
Users were recently hit by issues connected with the "Followers" feature on Bungie.net, it is not clear if this recent downtime is connected to that, while being a part of a wider update to make way for the Taken King expansion in September.
The studio revealed more of their plans for Destiny in the Year Two phase of its lifecycle, revealing some new storyline details and a trailer for the Taken King at Gamescom this week.