Predicting it will be the most profitable company in the world sounds absurd to me. But that's just me.
For some context, the most profitable company in the world in 2010 was Gazprom[1], the largest exporter of natural gas in the world, with 24,555.7 million.
EDIT: Gazprom was the most profitable in 2009, not 2010, as pointed out below.
[1] http://www.businessinsider.com/dropbox-revenue-2011-3
[2] http://money.cnn.com/magazines/fortune/global500/2010/perfor...
But with each incremental user, Dropbox's value increases in an e^x fashion.
For more on why I think so, here is a more detailed breakdown: http://marcgayle.com/how-dropbox-is-printing-money
There is no reason that Dropbox's growth will slow any time soon. It is a fabulous product, and has the referral system built-in.
It's the closest elixir to magic I have seen in recent times.
No other entity has amassed this amount of data before.
- virtual currency - daily deals - search integrated directly into the experience
and that's just off the top of my head
They have to figure out how to monetize a lot more $ per user to be very profitable in the long term.