How is this different from other apps like blip.me (besides for the obvious web vs mobile platform)? A year ago a bunch of friends and myself installed and began to use blip, but the novelty quickly wore off. Can't remember the last time I used it.
Is there any data that validates the notion that people will be leaving 5+ minute long messages for each other? I honestly can't remember the last time I left a voicemail for a friend/family, but that is purely anecdotal.
Anyhow, good luck!
For example, being far from family and friends, I love putting on my earphones, laying down and listening to my friends' messages.
The nice thing is that I can listen to these messages anytime my hands are busy but my brain isn't. Running, driving, biking, cooking are all more fun with a story from an old-friend in the background.