Their defensible advantage is two-fold:

1) they developed a technology that in theory should be easy to duplicate, but in practice is extremely hard. Large teams always mess this up (even world-class teams, e.g. at Microsoft, which has had several stabs at this), and small teams often don't have the skills to work with so many orthogonal elements at the high competence level required.

2) They have supportive users signed up on yearly contracts. That makes them very resistant to competition.

A Dropbox competitor would ahve to be 10x better for people to switch. That's hard to achieve.

I've been thinking about this lately as I use Dropbox more and transition from working at home to an office and find myself using 2 computers more.

A Dropbox competitor just needs to sync my app settings and stuff on top of what Dropbox does. I am gone the instant someone offers me a way to turn on my laptop and have an almost-replica of my workstation. Or upgrade phones, tablets or anything else.

Sync my <breed of device> is a lot better than just syncing some files across them.

I've been thinking the same thing recently. If the OS itself just lived on the cloud and had local copies it just updated, then your stuff would always be in 'sync' (including settings/apps).

Moreover, you could access the same OS using different platforms (mobile vs laptop) and it could behave appropriately. We're already moving towards this to some extent with more and more sync and push services.

NB Just to be clear, I'm not talking about a pure web-based OS and thin client (e.g all of google's products are like this). I mean being able connect to something in the sky that keeps it all in sync whenever you have a data connection.

Looks like you might be interested in VDI(Virtual Desktop Infrastructure).

Disclaimer: I'm ex-VMware employee.

as a semi-tangent; your scenario exactly describes why I'm buying kindle books, and I don't even own an actual kindle.

I am remote programmer which needless to say puts me in different coffee shops throughout the city. I ride the bus multiple times a day.

I'm able to switch devices seamlessly as I trek around, and kindle updates my "last known reading location" - go Amazon.

Your scenario is harder but quite exponentially more valuable as we start to see more and more smart devices.

I would hope rather than a single competitor there would be an open standard for this kind of file replication and then multiple implementations and service providers.

It's similar to Facebook: name recognition, everyone's on it so everyone's on it, etc.

And their stuff just works really well. They're also slowly cultivating a third party integrated apps ecosystem.

> They're also slowly cultivating a third party integrated apps ecosystem.

I think this is a big part of why Dropbox could warrant a high valuation. If Dropbox is simply "the platform" for file sync, then more integrated apps will come along with Dropbox support.

For example, the notes application I use on my Android phone (Epistle) uses Dropbox for sync. This is great because I always have those notes on my computer too. I think we'll see lots more of this in the mobile space.