Just because you've invented a communications service people want to use doesn't guarantee success. You need a critical mass of users before any communications service is valuable.
It's interesting to see how this is playing out with the mobile industry's Multimedia Messaging Service (MMS). In most markets, there are a dearth of MMS capable (and appropriately configured) handsets and interoperability issues between handsets. So, MMS has been slow to take off.
What's happened? Some enterprising entrepreneurs have launched Voice SMS, an audio messaging service that's taking off because it actually works with any handset, old or new.