You really hit the nail on the head. There's a solid business plan coupled with the three things backup needs. One thing to add: Tarsnap is even better than incrementals. It's snapshots that don't take up more space. That means that you can do things like delete an old archive since the newer ones don't rely on it for restore. Each archive works like a full backup even though it doesn't take up the storage space of a full backup!

I'm surprised that VC hasn't been banging down Colin's door. He has a workable business plan and a product that's wonderful. Tarsnap, in my opinion, should also have broad appeal to businesses. I know my company does a disk->tape thing, but often the tapes aren't so reliable, the whole setup is labor intensive, and it's stored in one location. Businesses are less hesitant to pay than consumers are and Tarsnap offers a lot of value.