Cloud will remove any privacy that you may still have when you store your own data on your own hard drive.
Not really. If store a encrypted sparse disk image in the cloud the data can be decrypted on the fly just on the client machine end. What is stored in the cloud is encrypted. NSA might be able to bust it if really wanted to, but pretty much private.
There is overhead in doing it, but can be done.
Stored as default iDisk. Yeah .... you are just spreading your 411 on the internet pipes in the clear.
And for what to save a few seconds?
Errr, access disk data over a random stretch of internet networking is generally going to be slower. Speed is not what is being sold by the cloud. It is primarily accessibility. If have 3 devices you can log into and use over the course of the day (e.g., home mac, touch on train to work , and work computer. ) , then it may be nice to have a mounted disk that follows you around where ever you log in.
If it is less that 8GB (or so) that could be a USB flash drive. (if all of the devices you log into allow you to plug in a USB flash drive. )
If you primarily accessing your from just one device... accessibility really isn't a big seller.
( if the cloud storage is large using it for off-site back-up is the other advantage. The "off site" being the primary attribute. Again speed may be a problem. Doing a restore of 100GB may be a problem too in terms of bandwidth caps too in addition to speed. )
If all this data is available for the good guys its also available for the bad guys and for misuse even from the people that should in theory be trusted.
If you don't want folks to see it, encrypt it.
The more relevant issue is that folks on the other side of the cloud can take it away. You can keep them from reading it, but they could possibly keep you from getting it. Can't run a decryption on something do not have access to.
The other major problem is that one of the other devices want to decrypt from won't have the software/keys to decrypt. If it is just one device where do reading pretty straightforward to make it almost painless to open read. If multiple devices then may/may not work as well. ( iPhone OS can read encrypted sparse image??? )