Comment by hereathomie

Just checked this myself on a MacPro. You can see the DropBox process kick in with CPU usage while opening big apps like Photoshop or Xcode. Not a lot on this MacPro (~3%), but it's always in time with an app opening. Oddly there's no corresponding disk access associated with the Dropbox process when looking at it on the Disk tab of Activity Monitor.

Would definitely like an explanation of what's going on here.