The photo-sharing service Twitpic announced Thursday it was shutting down, saying it faced an ultimatum from Twitter to abandon its trademark or lose access to the messaging service. Twitpic, launched in 2008, allowed users to post photographs on the messaging platform before Twitter adding its own photo-sharing option in 2011. Twitpic founder Noah Everett said the demand from Twitter came as a surprise, and that he had no option other than to end the service. A few weeks ago Twitter contacted our legal demanding that we abandon our trademark application or risk losing access to their API, he said, referring to the application programming interface.