I would be very interested in seeing if Dropbox does the same thing the author claims, but on non-Windows OSes. There are official Dropbox packages for OS X, Debian-based Linux distros, Fedora/Redhat and derivatives, and a source release for packaging the binary for other OSes. If the same or similar activity is seen on other OSes, something's afoot. If the issue only shows up on Windows, it's likely a Windows-only issue or quirk (but could still be nefarious and only targeting Windows users, though personally I'm not that paranoid).