One thing that's made me feel a bit better about Dropbox is my (admittedly geeky) setup for transparent encryption of everything that gets uploaded to DB. That way, even if a DB employee turns out to be evil, they can't get to my Quicken files and such.

In a nutshell, I created ~/MyDocs and ~/Dropbox/MyDocs folders and mounted an encfs virtual disk on top of them (via MacFUSE). That way, I just store everything in ~/MyDocs and it's transparently encrypted into my Dropbox and synced to all of my systems.