In a world where mash-up is the buzzword (or was it? Web 2.0 is not that cool anymore...), you would assume content is freely available to anyone. That you can take some data from Google, mash it up with something coming out of Facebook, Yahoo and so on.
That is true, up to a certain point.
The trick is that who owns the content (even the User Generated Content...) owns the content. It is as simple as that. If you do not own the content, you have to get it from somewhere else. The company that owns it can shut you down whenever they want. They do not even have to ask for your permission... You might have the APIs to technically access their content, but that is not nearly enough.
One example is what happened today at Facebook. They shut down an application that was simply creating an RSS feed of your stream. Granted, the app was overstepping some boundaries on Facebook privacy rules, but they could have just changed the rules, had they not like it.
This is exactly what happened in the Instant Messaging world (at least in mobile). Do you know any mobile IM company that made it? I don't... You can easily build a Yahoo Messenger integration, but when you go and sell it to a mobile operator they will ask you "do you have permission from Yahoo?". Nope? Go ask them and they will charge you. Everyone will do the same. The economics will never work when you are trying to sell a free app and you have to pay hard dollars to the content owner.
I could go on and on with examples. If you do not own the content and you are trying to build an application accessing it, you are putting your foot in a trap. As soon as you are successful, you sell it to someone or you get a lot of users, be sure the content owner will knock at your door asking for money. They will say you use too much of their bandwidth for free or that they changed their privacy rules or whatever. Bottom line: they will ask for money (rightly so, they own the content after all) and you will be screwed.
If you are a mobile operator and you do not own the content, you are also screwed... It is exactly the same thing as above. Build an integration and they will come after you. Your only option is to actually be the content owner. Take the user generated content first (it is easy and it is free, with no copyright issues), then you can add more. But be very careful on avoiding the content trap. The Internet Portals are just waiting for you to put your foot in the trap...