Music syncing, etc. was what I was referring to. I don't think they'll flame out right away, but in 5 years, what will they have that doesn't ship with your OS?
"Dropbox" is becoming a verb. They need to keep that up, so people ask if their device has Dropbox, or more appropriately (if incorrectly), ask if it "can Dropbox?"
It is a feature, a service, but so is Netflix, and Dropbox isn't encumbered by movie studios. They just have the neat "whoa this is almost magic" part.