After Microsoft announced its intentions to acquire Activision Blizzard, most fans of the two companies had already anticipated that its new flagship game releases would eventually make their way to Steam, too, with Call of Duty: Modern Warfare 2 being the prime candidate to set the precedent. This information was subsequently confirmed early on, though some still expected that Battle.net, Activision's premier gaming platform, would somehow enter the equation as well.One of the possibilities was that Call of Duty: Modern Warfare 2 might get a stripped-down launcher version of Battle.net that would run alongside Steam, like EA's Origin does, but the latest info suggests that this won't be the case after all. According to CharlieIntel, the Steam version of Modern Warfare 2 will not use Battle.net at all, but Activision ID instead, though there's another caveat in play as well.Namely, the Steam release of Modern Warfare 2 will necessitate that all players associate a mobile phone number with their Steam accounts, which will also need to be connected with their Activision ID codes, according to CharlieIntel. This measure isn't entirely unexpected, as many other contemporary multiplayer games like CS: GO also require players to enter their phone numbers in order to play competitive matches. While some may consider this a breach of privacy, the feature's advertised purpose is to reduce the number of smurf accounts and cheaters that are in circulation at any given time.
It's also worth pointing out that players can secure a batch of extra Modern Warfare 2 pre-order bonuses in Warzone and Vanguard titles right now, simply by connecting their Steam accounts with their Activision IDs ahead of time. Players are, therefore, heavily incentivized to start connecting their accounts early on and may wish to do so if they're hoping for as seamless a gaming experience as possible once the game comes out in late October.
This, too, sets a potential pattern for future Activision Blizzard releases on PC. Diablo 4 is coming to Xbox Game Pass, for example, alongside Modern Warfare 2. This means it's not impossible that Diablo 4 might also make its way to Steam down the line, and if it follows the same approach as Call of Duty is now apparently taking, this may be the first time that a modern Diablo game is officially playable on PC without Battle.net in tow.
The topic of using phone numbers to verify user accounts is, of course, potentially problematic. In 2020, a Genshin Impact glitch revealed users' phone numbers, which was a massive privacy breach for all people affected. While it's unlikely that the same thing would happen to Activision Blizzard, it's certainly not unthinkable and may even put some players off entirely.
Call of Duty: Modern Warfare 2 launches on October 28 for PC, PS4, PS5, Xbox One, and Xbox Series X/S.