Would you call "the killer app" something that everybody needs/uses? Because file sync is a GREAT feature, but many people have 1 computer, and wouldnt understa

Would you call "the killer app" something that everybody needs/uses? Because file sync is a GREAT feature, but many people have 1 computer, and wouldnt understand syncing with a smart phone via an app anyway. Also, I would say while the sync is awesome, some of the other dropbox features are actually why I use the product instead of other more private options. (instantly link to anyone anything in the folders you have? very nice. +constant free space via different referral games.)