Pownce.com - Is it really necessary?

Today I found Pownce which I for some reason haven't seen before. It's a web2.0 app for sharing photos, invitations, files or text with your friends and contacts. It's still in invitation only testing mode, so I haven't tested the service. It looks good but I'm not sure that this alone will be interesting enough to be a really successful startup. What is interesting is that they have a clientside application as well, that take use of the Adobe Air system, so you can download a client for both Mac and Windows. Since I haven't seen Air that much in action yet, I'm looking forward to Pownce just to give Air a try.

As I see it to much of the functionality can be found in competing, a bit similar webapps, as in a MSN, Yahoo or facebook group, and I don't think people will bother signing up for just some smaller extra features. If they make a facebook / yahoo / google widget out of it, I'd say it would be more of an interesting bet. A mobile solution for sharing would also make this a much more interesting startup to me.