I would agree that I think this is mostly a business decision. And it seems to be the same business decision that almost every player in this space has made.
But it relies on the user trusting the vendor with their data. The user can't audit Dropboxes internal systems. They can't rely on the fact that security researchers will audit the client, and ensure that data is transmitted securely.
So it comes down to trust. I can't really see how I can trust dropbox when they think having board members who advocate warrantless surveillance is reasonable.
They chose a board member who is in favor of providing their users data, without the need for a warrant.
In contrast, Apple have made a stand against government access to their users data outside of legal requirements. Their service has similar issues, but I'd be more likely to place my trust in Apple than Dropbox because they have some track record of fighting back.
Ideally, what I'd like to see is optional client-side encryption that was externally audited. Unfortunately I think it's a feature that most users don't see as critical.