The personal clouds I'm interested in are about all of the information that sloughs off us, not trying to build new interfaces, but providing the tools for people to gather and organize and collect all of the information about themselves that they're currently giving away.
And the dust cloud metaphor here is also useful because back in the late .com boom there was a Berkeley company called "Dust" that promised sensors everywhere, like dust. They over-promised (or just sewed up the patent space and are waiting for someone else to come along and actually implement it, I don't know), and we're still waiting on that reality, but it's coming slowly.