How to stream my video files from the cloud?
You could try Jungle Disk. It's a pay service, but it gets you what you want - a locally mountable cloud drive. It can store data locally as well, like Dropbox, but you can configure it as an archive, with no local storage used. It uses Amazon S3 or Rackspace as the backend storage, so you pay a $3/month fee, plus an amount per GB per month.

I believe there are similar services out there, and you can just use S3 directly and get something like Panic's Transmit to mount the S3 storage as a local volume.