I don't own a Mac and I'm married already so might opinion might not matter that much, but if I was getting married, I'd want the videographer to set this up. Somehow I don't feel comfortable buying this kind of a thing for $99, but if a videographer charged me $99 to have a Macbook (better yet an iPad!) at my wedding where people could easily record video messages, I'd feel much better about it. The difference is that it becomes the videographer's problem if something breaks. Otherwise, if I bought it and brought my own computer to set it up I would (a) worry that somebody stole my beloved laptop and (b) something went wrong and nobody is actually able to record the videos. Targeting this at videographers might not bring in as much dough, but it seems to me it would have a higher chance of having satisfied end clients.
This. I was worried about so many other things on my wedding day. The last thing I'd want to fret over was doing tech support for a laptop and piece of video software. Most of my groomsmen were top-notch tech guys and I wouldn't even want them to worry about it. They were there for me, my wife, and our wedding day, not to play help desk tech.
But if this was something our videographer or photographer had offered I would've jumped on it in an instant.
The advantage of having a direct-to-consumer approach is that I can see a market for non-wedding occasions, where there is no official videographer. Baby showers, graduations, retirement parties, it wouldn't surprise me if some people even wanted it for a funeral/memorial. It's a pretty neat idea.
[Edit: just thought of another one - military people posted overseas, I can see people at the family gatherings like Thanksgiving wanting to send individual video greetings]
If hardware were included, I think this would be perfect for the exact reasons you specified. The number of people comfortable enough with computers to deploy something like this for such an important task is vanishingly small when compared to the number of people who would pay a little extra to a videographer to bring a ready-made kiosk unit to the wedding.
