Personally, I love using cloud storage if I want to move data from one computer to another. Of course, if I have a flash drive ready, that's usually a faster solution. Let's face it though, most people (myself included) don't carry a drive where ever they go. For me, that's where cloud storage comes in handy. Also, cloud storage is obviously better when it comes to redistributing files to a large number of computers.
As for long term storage, I agree that you're better off using you own CDs, DVDs, NAS units, added hard drives, ect. That's pretty much the only option that allows you to be in control of your own data. Services like RapidShare, Amazon, Google Cloud, ect. certainly aren't good solutions for backups, as articles like this one shows.