Because if you stop serving up the remote reference before it gets requested by a particular client, it won't be there. If it's archived {immediately,on first

Because if you stop serving up the remote reference before it gets requested by a particular client, it won't be there. If it's archived {immediately,on first request} permanently thereafter, there's now another copy outwith your control. Edit: moreover, the images are requested locally by the user's browser. Google doesn't get a look at them at any point[1]. Whereas now, they get a permanent copy for free, because they're doing you such a favour! [1] Directly, anyway. I guess they could use js to get the requests and headers and submit them back to the mothership, but on slow connections that could be pretty obvious.