We all know this number by heart: Facebook has a staggering 500 million subscribers with no signs of slowing down. But, what if I told you there's another social network with 280 million subscribers? Granted it would be no where near the size of Facebook. But, 280 million people would get your attention wouldn't it?

Well, sit up! No, there's no alternate social network that big. But, when you add up the subscribers of all those niche social networking groups based on special interests (in other words, NOT Facebook or Twitter); it adds up to an also staggering number of 280 million people worldwide (this figure courtesy CommScore, by the way, based on July 2010 numbers).

This is so 1920's to me. Let's rewind the history of magazines for a minute.

Back in the 1920's, general interest magazines like "Life", "Reader's Digest" and "The Saturday Evening Post" ruled. But while American audiences were holding up Norman Rockwell covers as a fanciful and collective mirror of themselves, Bill Ziff and Bernard Davis were ignoring all that and launched a magazine devoted to flying called Popular Aviation (eventually it would change hands and names and actually be called "Flying" and by the way, it still exists today).

The Ziff-Davis partnership would lead to a long and rich history of magazine titles based on hobbies and special interests. Over the years, not mass audiences - but niche ones - would enjoy magazines like "Car and Driver", "Stereo Review", "PC Magazine" and "Popular Mechanics" just to name a few.

I can't help but make a connection between Facebook and The Saturday Evening Post. For that matter, isn't Digg just Reader's Digest 2.0? Meanwhile, take a look at the number of social networking sites from this Wikipedia entry. It's in no way exhaustive. For example, it doesn't include GoFishN, as recently highlighted in a Bloomberg News article. GoFishN is a social networking site just for fishing enthusiasists. There's also Eon for Babyboomers, CafeMom for mothers, Library Thing for book lovers, PassportStamp for world travelers or at least wannabes, Cake Financial for personal investors, etc.

If past is prologue, these niche networks will rise and fall like South American potentates. Ziff-Davis had a great run for about 80 years. But make no mistake, it's gone. (Disclaimer alert: I worked for Ziff Davis Television from 1996 - 1999).

However, walk into any bookstore or newstand and you will still find racks and racks of special interest magazines (like INC Magazine, for example). The Saturday Evening Post is gone. Life Magazine exists, sort of, but it's hardly the pop culture icon it once was. Ditto for Reader's Digest.

The walkaway from all of this is that content really is king. Yes, people want connection. But, its content that connects them. This is a truth that transcends the preferred media platform of the moment.

You can follow me on Twitter @oricchio and now I'm off to read the latest issue of BBC History Magazine.