Nothin' like a good old chicken and egg debate.
I recommend 4gb of ram for any new 64-bit system build, regardless of what they're running on it. Mostly because ram is so cheap anyways, most people wouldn't notice. Partially because there's really no telling what the next "must-have" bit of software is going to come out. Typical users aren't going to need that extra ram for quite a while, but it sure ain't gonna hurt them. In the event that something comes out with a reason to use more, they'll be safe.
As for gamers and hardware enthusiasts (like the majority here), we're all ahead of the curve for the most part. The apps that we use are also ahead of the curve. Many games can eat up that first 2GB without really blinking an eye. Rendering 3d models, photoshop, video editing, virtual machines, even folding can utilize extra ram as well. Back in the day dual core processors were made to "DO MORE". Why should I close out my apps if I want to game? Most of the time I have a second monitor running performance monitoring, temp sensors, a web browser, and folding on my 2nd gpu. Thank GOD I have the 6GB of ram, because I watch it sneak up into the 5GB range rather often.
I understand the statement for the mainstream users of the world. No, they probably don't need 4GB of ram. But I do.