I work for a very big, bureaucratic company. Communication tool needs are really different for different scales of companies.
I live in the San Francisco Bay Area, and have a lab across the bay with a couple of coworkers that I generally go to once or twice a week. My current supervisor is in Atlanta; I've never met him in person. I worked for my previous supervisor for a year before I met him. I've worked for my director for about 5 years (he's in Indianapolis, and I've never met him in person.) We work with a bunch of developers and operations folks around the US and some in Eurasia. We use all those tools, and they've got different purposes. For maintaining documentation that sticks around, sometimes it's useful to have wikis and similar web sites that users can edit; for shorter-term documentation, we use tools that are designed for faster communication, and haven't really figured out how to handle the problem of obsolete chunks of information, which is harder on less-aggressively-managed systems.
Social networks are another point in the communications spectrum. For dealing with bug reports or feature suggestions from users, they're less formal than ticket tracking systems, but sometimes that's useful. If some developer wants to steal my ideas or listen to my rants\\\\ insightful comments, that's just fine. We've been starting to do a lot more with social networks, and we'll see how well it handles the problems of disposing of conversations that don't need to be kept around or are no longer current, or keeping information accessible that is current.