[UPDATE:] EA responded to a Kotaku inquiry about Darkspore thusly:
Maxis continues to support Darkspore and its servers. We recently resolved a problem where players were having issues connecting to the game. The post in question came from a moderator who is not an employee of EA. That post has been updated to reflect accurate information. Players experiencing technical issues should contact help.ea.com for customer support.
Steam is in the process of relisting Darkspore on their service. It should be returning in the near future.
The Diablo-clone Darkspore seems to have been a litmus test for Diablo III. Its always-online requirements, even in single-player, was a harbinger of things to come as EA tried to rebrand it as "part of the experience" rather than DRM.
According to GameTrailers, "Recently, 'Error 3' has been popping up in the game, which prevents players from saving any changes made on their heroes. It's a server-side issue and players will have to wait for it to be resolved." Bugs that have kept players out of the game for extended lengths of time are not new, but this one is more problematic, because it doesn't appear it will ever be fixed.
From Darkspore's official forum: "Darkspore is no longer developed. It is for almost all intents & purposes an abandoned title. ... Error 73003 has gone unfixed & remains an issue. Error Code 3 has arisen for the majority/all & remains an issue."
Steam has pulled the now unplayable game from its store. Darkspore can still be purchased from Origin for $19.99 as of the time of this writing.