They wouldn't lose too much of their existing customers. Are you implying that massive data collection and advertiser interest are
bad?
Most people really don't give a shit about massive data collection. I mean, sure, everyone's a Reddit slacktivist nowadays, throwing around words like "spying!" and "privacy!" but no one really cares, or else we'd all be using rsync + ftp and BitMessage and all that idealistic free software stuff that RMS peddles. People just want to seem special and cool and smart and advanced when they post about how EVIL the government is for spying on all of us. The art of saying "I don't use Facebook; they sell my info to advertisers", then turning around to use Google products (which are fucking unavoidable on the Internet, by the way, did you know fucking ReCaptcha is owned by Google? You'd have to completely avoid the Internet to avoid Google at this point) , is the 2014 spin on the 1990s art of saying "I don't own a television".
We use Chrome and Gmail and Facebook and OS X and Amazon and what-not, because the net benefit of having really convenient software developed by teams of hundreds (thousands, even, in huge cases like Google/FB) talented professionals that are putting in $120K / year's worth of effort beats the net cost of having to pay for that $120K by letting Facebook give advertisers all your user data to make up for the costs of developing and operating such convenient software (and whatever profit FB is hoping to make -- people don't start businesses out of the goodness in their hearts). I mean, what's the alternative? Paying for the $6 per user per year that Facebook makes? Would you really rather pay for these services than just aid in letting the advertisers know that 67% of young (18-34) males in New York City prefer Macy's over JC Penney? Is it really that significant, your tiny, indistinguishable contribution to our advertising overlords that isn't even tied to your personal identity? It's not like they know that specifically Omar Hegazy and Xerophyte clicked on this ad over that ad in A/B tests; they don't give a shit about the specific identities and that would be truly creepy. No, they obviously care more about aggregate statistics, like overall click through rate and what-not. And when you're just another brick in the wall of statistical analysis, is it really all that creepy? Do they really know all that much specifically about you?)?
So, people don't really care about privacy, and Dropbox wouldn't lose a huge chunk of their customers. Or else, Facebook and Google and Apple and what-not would've lost a huge chunk of their customers.
I agree, though, about the enterprise market. Enterprise is smaller than consumer-facing, because the set of all professionals in a certain vertical is much smaller the set of everyone. That means that spying on the enterprise market is much more personal and tied to identity than spying on everyone as a whole. So it really does lose you customers in enterprise. Also it's much easier just to charge people directly for money in enterprise; usually verticals have a greater demand for a proper solution than horizontals, cause they're a much more specific market to target and so their biggest pain points are easier to solve. People really would pay $6 a year, and even more, for a product that truly understands what their specific problem is.
But I disagree that enterprise is where all the moolah is. I just think that it's much, much harder to make moolah in consumer-facing software, and all the moolah in consumer-facing software goes to a select few very well-known winners. But if you become one of those winners, then you have much more money and historical recognition than any boring old enterprise company will get you.
It's really very hard to nail down "What's a problem that everyone is having but no one has solved?" -- but when you do nail it down, oh boy, you just solved everybody's problem, and it gets you the quickest company to reach $150bn valuation in ever and the founder becomes the youngest billionaire in the world. I think, if Drew Houston and Co. went down the consumer-facing route, they'd be playing their chips on the assumption that they really struck gold with answering that seemingly unanswerable question. And given how far Dropbox has gone in the consumer market, I wouldn't hold it against them for taking that risk.
That being said, they do seem like they're saving some of their chips for the enterprise route. So if they really were worried about ruining enterprise trust by being yet another consumer-facing company that gobbles all your data and feeds it back to advertisers, they'd just do the other thing I suggested - sell hard drive space. But something tells me Dropbox is trying to be more.