Actually, Bitcasa's offering is extremely good. It has features and advantages that none of the other similar services (Dropbox, Skydrive, Google Drive) offer:
1) You can "cloudify" any folder transparently (including removable media and network shares).
2) You can cache any amount of data locally (managed automatically) up to the amount of free space on the local machine. Actual data volume in cloudified folders is unlimited.
3) It's all you can eat (but if you're going to abuse it you're going to need a LOT of internet bandwidth.
Having had a quick play with it, it is quite awesome. There are a couple of limitations:
1) No linux client. Tthis makes it mostly useless to me - having to run Windows in a VM to keep my folders in sync is a bit too much of a requirement. It also makes it less easy to keep the data encrypted (surely no sane person would keep their data in the cloud unencrypted?) and versioned (I have to stack cryptfs and copyfs on top, and then cloudify the bottom layer).
2) No Android client.
The lack of Linux and Android support makes it not yet ready to replace Dropbox for me. Once those two platforms are supported, I'll be sold.
The only concern is how they plan to monetize it - all you can eat is a lot of disks to be maintaining without revenues. Without that, the service might just disappear with little or no warning, taking all the data with it. Even if there is reasonable warning, how much of a run on local disk supplies is it going to cause, and how long is downloading, say, 10TB going to take (i.e. how much of a warning are you going to need)?