You can either tear out your hair when a disaster strikes your hard drive or you can prepare for it ahead of time, but data loss is as inevitable as death and taxes. An online backup service is one of the best ways to protect yourself against such threats as a crashed hard drive or accidental deletion. Natural disasters such as fires, floods, and earthquakes can also spell the end of your digital media and documents. Even if you're among the very few who diligently perform local backups at regular intervals, you could still lose data if you don't store backups offsite.
Backblaze earned praise from many of you for being easy to set up, even for non-technical people. It's built for people who want to get their data backed up, without being forced to search for error codes and cryptic status messages whenever something goes wrong. To that point, Backblaze backs up just about everything on your system. You get some control over what's backed up and what isn't, but the point is to be fast, easy, and hands-off, so everything on your system—documents, music, video, external drives you have plugged in, just about anything. Instead of telling what they do back up, Backblaze actually has a special page dedicated to what they don't back up instead. Backblaze offers unlimited storage for your backed up data, and while by default it only backs up files smaller than 4GB, you can bump that up if you need to. Like other online backup services, it runs in the background, backing up your data all the time (or when you schedule it to, if you prefer), and your data is encrypted so only you have access to it. It supports Windows and OS X, and is smart enough to de-dupe data, do incremental backups, and keep backup processes low on system resources. You can read more about Backblaze's features here.
I'm using YouTube offline feature on my Android device, so that I can playback the offline videos within the YouTube app even there is no internet connection. When I searched for any of the video files, I can't find them on device/SD card memory. Are they encrypting the file so that it can be played only with YouTube app? Does anyone know the specific folder for offline video data?
SpiderOak's beauty is that it's a combination cloud syncing and storage service as well as a backup client all in one. Unlike some of the other services though, you'll have to pay for the storage you use. You get 2GB for free just for signing up, and you can get up to 10GB by referring friends. SpiderOak Plus nets you 100GB for $10/mo to use for syncing and backups, and every 100GB after that is another $10/mo. Plus, you can connect as many computers to any SpiderOak account as you want, so you're not paying by the system. You can read more about SpiderOak's plans here.