Twitpic

 Twitpic  was a photo silo designed for sharing photos on Twitter. It will be shut down October 25, 2014.

Usernames
Twitpic re-uses Twitter usernames.

Feeds
Public feeds are available of Twitpic users' posts, e.g. for user @aplusk:
 * http://twitpic.com/photos/aplusk/feed.rss

Shut down

 * 2014-09-25 TwitPic announced it would be shut down, but on 2014-09-18 TwitPic stated it was acquired and would not be shut down.
 * "We're happy to announce we've been acquired and Twitpic will live on! We will post more details as we can disclose them"
 * Original reason for the shutdown announcement: "A few weeks ago Twitter contacted our legal demanding that we abandon our trademark application or risk losing access to their API. [..] Unfortunately we do not have the resources to fend off a large company like Twitter to maintain our mark which we believe whole heartedly is rightfully ours. Therefore, we have decided to shut down Twitpic."
 * Data export: "You will be able to export all your photos and videos. We’ll let everyone know when this feature is live in the next few days."
 * 2014-10-25 Twitpic’s Future "[…] we have reached an agreement with Twitter to give them the Twitpic domain and photo archive, thus keeping the photos and links alive for the time being." Emphasis added, thus implying domain and permalinks still at risk.
 * 2017-12-30 Twitpic.com now redirects to Twitter.com
 * 2018-03-05 Twitpic.com URLS for photos apparently still resolve directly to the photo though the prior UI for the service is gone.