I think it was around 1996 that I declared that Advertising was the Killer App. of the Internet at presentation I made at the National Association of Broadcasters.  I still believe that although, in reality people to people communication is the killer application and advertising is just the way must companies try to monetize that (I emphases “try”).  But because you have an audience, it does not mean you can effectively advertise.  Just stand on the ledge of a building and threaten to jump.  You will soon have a large audience but even if you were a logo’ed shirt, you will have a hard time turning this into an opportunity to make money.  And such is the problem of MySpace (which I don’t really care for) and Facebook (which I really like).  Effective advertising on the internet is a challenge for most.  It works well for search as has been demonstrated by Google but that is direct response advertising.  Brand advertising is even a greater challenge to this new medium.  Heavy does a great job (I am on the board and this post is not really about plugging heavy)  but  that is helped because the company is provides short form entertainment content.  I believe that social networks can make money of course with advertising, just not the kind of money that would justify the prices that have and will probably be paid for their stock.  But then again I said that about Google.