Currently I don't really use cloud storage, it's cheaper for me to colocate a 2U stuffed with disks and buy transit.
Primarily though I store media. I have (for a home user) large amounts of high resolution (lossless audio, RAW images, high bitrate (even ProRes) video) media that I like to keep for archival and transcoding but don't need for playback. I want to store the original media somewhere safe and cheap but have the ability to transcode it to a format suitable for playback/streaming on demand.
Actually it just occurred to me that it might be worth you talking to the folks at Plex (https://plex.tv) about this too, as they're working on their Cloud product and need more places for their users to store media.