I'd like some way to preserve the external images linked in questions. Then when the original image is deleted (hopefully indicated by some HTTP error code, even if some error image is returned in the response as well), maybe somehow the (future non-read-only) API can fix that.
Preserving the images could be done using the data dump as well. But maybe the API is more suitable for that? And surely the data dump cannot be used to change image links into something new.
I myself use Skitch for image grabbing and hosting, which has been in beta for years. However, it probably won't be free in the future, hence a lot of pictures might disappear from the web in general, and from the Trilogy sites. I always put a link to where I used my own pictures into the comments at Skitch, so I could upload them to some other service if needed (and if Skitch warns its user in time). At that time I would still need to manually edit all my posts to refer to the new service. And I doubt many others would do that too.
Update: now that new images are uploaded to Imgur: ready, start, go! ;-)
(But, there might be an issue with hotlinking that is no hotlinking anymore.)