[tokenadult]

File sharing is the type of thing where you can't just rely on first-mover-advantage.

Yes, especially in a market where there are many, many users of computers who might have occasion to share files who have not used (or even heard of) any of the available file-sharing solutions yet. I am a sporadic user of Dropbox strictly for back-up of documents I produce, and a moderately frequent user of Google Docs for collaborative editing who knows a lot of other Google Docs users. I could see Google making huge gains in market share, turning it into tomorrow's "first mover" from the point of view of most users, for a file-sharing service.

[lionhearted]

I didn't get why Dropbox was so popular when I was using it the same way you are right now. Okay, it's a convenient way to make backups, but so what?

Then I started using it for sharing. Man, it's magic - I've never had it be so painless to share things. I can put a folder in my dropbox, share it to a few emails, and then everyone just has it later in the day. Man, that's cool. I can also create unlimited of those folders easily to control who gets what documents/files. It's a bloody miracle, Dropbox is. The backup feature is really second fiddle to sharing, it's just to make it useful enough for you to try it before you need to share, so that you discover sharing and fall in love with the product.