It appears that, on sid at least, there is now a precompiled Dropbox binary in the Debian repos. Thus, you will no longer need to compile from source (although that option is still available, of course); instead, you can simply install it like so:
# aptitude install nautilus-dropbox
The Dropbox package is listed in the non-free repository, as indeed it is not software that complies with Debian’s software freedom guidelines. A non-proprietary alternative would be welcome, but for the time being it’s now possible to install Dropbox through APT on Debian.