I'm not sure anyone explicitly said it would have online multiplayer, but I'm also not sure anyone explicitly said Ghostbusters for the PC wouldn't. Some are saying explicit things about the game's authentication requirement, too.
Ghostbusters enthusiast site Ecto-Web did a compare of the system requirements and, while noting an Internet connection is needed to authenticate the game, it has no point after that. Says Ecto-Web:
Which of the three realistic versions is getting the shaft? If you said, "PC", you're a winner! Compare the feature list of the PC with that of the PS3 and Xbox 360 and you'll notice that the PC does NOT have: Online multiplayer co-op (or any online activities at all!) and downloadable content, even though a PC game not only is capable of such features, PC gaming INVENTED those features!
Seems like a reasonable enough expectation, however, who's gonna pay for the space to host and find games, or the bandwidth to pipe you the DLC?
Behind the scenes, it may be a misnomer to call it DRM, but there is a copy protection scheme - you've got to authenticate your disc the first time you play the game, and that requires Interwebs. If the basic expectation of a PC gamer is that he has an internet connection, then it's a basic expectation, by now, that most PC games should have a multiplayer component.
Anyway, the game is out on Tuesday (Only if you live in North America - AU Ed). If this was a determining factor in your decision to buy, consider yourself notified.
Ghostbusters Video Game Box Back & Specs [Ecto-Web, thanks CyborgMatt and Grady]