I think that if a startup made encryption and data security a priority and had the amount of funding it takes to break the enterprise market, they'd start to slowly (as usual in the enterprise space) make more headway and gain acceptance in this area. IT actually likes to offload things when they have a reasonable assurance of control.

Tarsnap is a good starting point, but it's CLI, doesn't work on Windows, and isn't really geared to big businesses.