They're saying they have essentially one revenue source. A lack of diversity in income sources is the risk factor. Compare to Microsoft: Various consumer software options, OEM OS licenses, government contracts, support contracts, physical hardware (Xbox), licensing for game publishers, Azure, etc.
Dropbox has one revenue source, and it's primarily fed by consumers (11 million at that, per this filing). A loss of 1 million users is a loss of 100 million in revenue for them, but doesn't correspond to a drastic reduction in their costs (due to the number of non-paying users).
Dropbox has one revenue source, and it's primarily fed by consumers (11 million at that, per this filing). A loss of 1 million users is a loss of 100 million in revenue for them, but doesn't correspond to a drastic reduction in their costs (due to the number of non-paying users).