The number one reason to download the entire YouTube channel is that you’re going to have offline access to them. If you want to catch up on your favorite shows but you’re going to be without internet for a while you may want to have a way to do it without the internet. Being able to get access wherever you happen to be, directly on your device, is going to be an important step. It’s going to make sure that you have something to do during that time that you’re away from internet access or not wanting to use your internet access (which is another great reason).
Bitcasa starts you off with 10GB for free, but $100/yr throws the floodgates open and gets you unlimited storage for anything you want to sync, share, or back up. Plus, you can connect as many computers or devices to your account as you choose, so you don't pay by the PC. It's client isn't quite as robust as some of the other tools here, but if you're more interested in a flat fee for unlimited space and you can handle the details of which files go where and when, it's a solid option. You can read more about Bitcasa's pricing here.
Real time: Real-time backup means that files are backed up whenever they change, usually upon creation or save. It’s also called mirroring and is handy for keeping an immediately available copy of rapidly changing data sets. For less volatile data sets, the payoff doesn’t compensate for the drain on system resources. Instead, scheduling should be used.