Some of those that recently bought GSC Game World's S.TA.L.K.E.R.: Clear Sky and Egosoft's X3: Terran Conflict were temporarily unable to activate and play those games, due to reportedly resolved problems with the TAGES-run authentication servers.
Both games utilize TAGES DRM to enforce a 5-machine activation limit, and received a resurgence of attention as they were featured in the Steam Holiday Sale. The promotion saw 10-75% discounts on games sold via the PC digital distribution service.
Upon attempting to run either game, first-time players were told that they needed to activate their copy with a serial number. Some attempts were met with a network timeout error, while others, such as Shacker Stucky_101, report they that had no problems.
The issues began cropping up en masse between December 26 and 31, going by two separate threads on the Steam forums. The problem also spawned a lengthy thread over at the offical X3: Terran Conflict forums.
The problem was reportedly resolved as of this morning, as both Shacknews and many posters in the Steam thread were able to successfully activate S.T.A.L.K.E.R.: Clear Sky.
Though most of the complaints stemmed from Steam users, it is thought that the server issues affected all new buyers of the above games, with the Steam Holiday Sale bringing the issue to the attention of more Steam users than normal.
The issues have caused many to question the need for third-party DRM on Steam, which is itself a form of digital rights management as players must sign-in at least once to download and activate their purchase. Only certain Steam-sold games feature third-party DRM, with a game's publisher ultimately deciding if it will sport third-party DRM.
Both S.T.A.L.K.E.R.: Clear Sky and X3 were self-published on Steam by GSC and Egosoft, respectively. Ubisoft is another DRM-utilizing Steam publisher, while EA surprisingly removed DRM from its Steam offerings when they debuted in December.
Thanks to Shacker Bulaba0 for the tip.