I understand the fundamental argument here, but were people really thinking that twitpic was some kind of online image archive? Are there lots of people operating on the assumption that twitpic was going to be forever available and available as an image catalog?
I see twitpic, imgur, Facebook, and even services like flickr as temporary methods to share photos online. Berating twitpic for not having an export seems a little bit odd to me.
Indeed, and for that reason it's a shame why only few services allow seamless synchronization. Apparently, you can show Google Drive photos in Google Plus, but not with an Apps account (which I have). Dropbox currently comes closest: I can add photos from files/folders to Dropbox photo albums. This is really the nicest way of photo sharing: I can just copy a photo to my Dropbox folder, share it in an album as in Flickr. My local Dropbox folder is backed up through time machine, etc.
Of course, Dropbox' album functionality is currently severely limited. I'd really like to see them expand it, or Google to make their service smoother and generally available, or some startup that makes photo albums from your Dropbox/Drive/OneDrive folders.
These are really not the same types of service.
* Twitpic was for posting photos incline on Twitter in the days before Twitter added that feature. This is a very specific function: it's not a photo storage site, and never has been.
* Imgur was originally for sharing photos on reddit, but not inline: you go to Imgur to view them. But there's no guarantee that your photos won't be deleted for one reason or another (as the celebrity nudes were deleted).
* Facebook is for sharing photos with friends. There's every expectation that they'll be available as long as you have a Facebook account, and you can download them. However, there's no guarantee that your original photos will be saved in their original resolution. Again, it's not an archival back-up site.
They are different sites, set up to provide different functions.