After upgrading from OSX 10.8.x to 10.9 (Mavericks), encfs recipe is broken. First of all you have to fix a problem with a library header:
sudo ln -s /usr/include/sys/_endian.h /usr/include/sys/endian.h
then you can install encfs using this remote brew recipe:
brew reinstall https://gist.github.com/ghibble/7297078/raw/cae1ff000a5e1cfc670f5b7a611279ed494b63af/encfs.rb
It's also possible that you have to fix fuse4x installation before being able to use encfs (I had to do it):
sudo /bin/cp -rfX /usr/local/Cellar/fuse4x-kext/0.9.2/Library/Extensions/fuse4x.kext /Library/Extensions sudo chmod +s /Library/Extensions/fuse4x.kext/Support/load_fuse4x
That's it! Please note that this is just a workaround (thanks to Giovanni Bajo for suggesting me the symlink fix). Please also note that this recipe uses fuse4x library and not the most updated osxfuse (but it works, anyway). Some other users reported me that there is a fix for the original brew recipe, and this one uses osxfuse. You can find it here https://gist.github.com/defunctzombie/7324625 but I haven't tested it yet.
Update: to fully integrate encfs with OSX, I also suggest to follow this nice guide http://www.maketecheasier.com/install-encfs-mac/