Over the past year, the online support for a list of games has stopped. This means that the online component of these games will no longer be accessible, along with any achievements or unlockables attached to it. The support for these games wasn't cut off all at once and doesn't necessarily affect all platforms.
Many of the titles are old and no longer usable on modern hardware, with some reaching back to the Wii era. At the risk of aging myself, a good portion of the list reads like a rap sheet of wasted hours. Tom Clancy's Endwar and World in Conflict are two of the best. Ghost Recon Advanced Warfighter 2, H.A.W.X. 2, and Beyond Good and Evil are just some of the games that are no longer available on the PS3 or 360.
This wouldn't feel like a big deal, except that it's effectively destroying large parts of gaming history. When publishers decide to no longer support games with large online components, especially when they're so hesitant to allow communities access to the tools to keep them alive, they get lost in the sands of time.
It's understandable that a company can't be expected to keep a game on life support forever, but some of these games represent some significant accomplishments on behalf of the people developing them. It seems like a net loss for gaming history to have those assets erased forever.