I built http://greetingbin.com as a platform for uploading images of greeting cards along with some metadata to the cloud. Then you could throw the card out and still have a digital copy of it. Needless to say, I have no users. Granted, I didn't do any marketing, but I realized that in actuality I never used the product myself, so why would anyone else use it?
1> After uploading all sides of a greeting card, use some animation/visualization that will allow you to interact with a single card by clicking/swiping.
2> Allow this to be embedded into FB/Twitter
3> Make the service free - the most likely monetisation will be advertising, so it's all about MAU
