The ways you can criticize the president continue to grow more limited on Flickr. If the first rule was "don't post too many political comments on White House photos," the second seems to be "no caricatures."
It originally looked like Firas Alkhateeb, a Palestinian American University of Illinois student, had removed the caricature himself. But it turns out Flickr "removed the Joker image due to copyright-infringement concerns." Because that doctored Time cover (above) could totally be confused with the copyrighted original, as opposed to, say, a transformative political satire!
As the Slashdot crowd has been quick to point out, there are all sorts of copyrighted and often doctored images involving George W. Bush (and others - NSFW) on Flickr. Meanwhile, Obama has opened the door to lucrative government contracts for the Yahoo-owned photo-sharing site.
Yes, it's easy to refute that conspiracy theory; the CEO of Yahoo has donated to Republicans Bush, John McCain and California gubernatorial candidate Meg Whitman, as photographer Thomas Hawk has pointed out. And yet Flickr's explanation remains completely ludicrous; as ludicrous as, say, nuking photos of paying customers with no warnings and no backups, or allowing someone to irreversibly delete an account because they can guess the account-holders birthday or other security-question answer.