[rfolstad]

dropbox did something useful. It made it easy to share files across platforms and the web. This is a feature that should be part of your calendar software to allow people to create calendar entries in your calendar and see availability.

[klabb3]

Not really, depending on how you define sharing. Dropbox added sharing as a feature much later. Their initial product was automatic cloud based backup and sync, across desktop devices. You can still tell by the UX and pricing model - sharing is slightly awkward and I believe rate limited.