TechCrunch had a post today about how iPhone apps aren't taking advantage of network effects yet, and that reminded me of a thought I had a while ago about iPhone apps lack of viral distribution functionality as well. It's a different aspect of the same sort of concept. (By the way, I don't agree with Arrington on everything, but that mobile apps and websites will have to have a supporting PC-based website is dead on, and something I've been mentioning quite a bit lately).
Remember Vindigo? They're still around, but I'm talking about the original Palm app from the turn of the century, which I included a screenshot of above (thanks interweb for keeping that around!). Right on the home screen, Vindigo encouraged its users to give the application to another Palm user. At the time it was an incredible innovation because it took advantage of the Palm's ability to share apps (by "beaming" them with the IR port), which many people didn't know was possible, and had a revenue model that didn't require the app to be purchased.
Every iPhone app - especially the free ones that are ad-supported - should have big, bright buttons on the main interface for "sharing" the application. Those iTunes style links starting with "phobos" (the ones that piss me off on my iTunes-less Ubuntu computer) work just fine and dandy on an iPhone, bringing up the AppStore for instant on-device downloads. It'd be trivial for apps to create an SMS or Email message to be sent with a pre-included link to the iTunes store, ready to send to one or more friends, and in the age of social networking, having the ability to send your message to any of your Facebook or MySpace friends would be invaluable as well.
This yet another example of stuff I was writing about over five years ago. So much has changed and yet in many ways, so much of mobility still remains constant. It also reminds you of how much an iPhone is really little more than the next generation of PDAs. (Face it Jobs, Sculley was right - he was just a couple decades too early.)