brew doctor and libmacfuse/libosxfuse

gistfile1.txt

If you see...

Warning: Unbrewed dylibs were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected dylibs:
    /usr/local/lib/libmacfuse_i32.2.dylib    /usr/local/lib/libmacfuse_i64.2.dylib    /usr/local/lib/libosxfuse_i32.2.dylib    /usr/local/lib/libosxfuse_i64.2.dylib
Warning: Unbrewed .la files were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected .la files:
    /usr/local/lib/libosxfuse_i32.la    /usr/local/lib/libosxfuse_i64.la
Warning: Unbrewed .pc files were found in /usr/local/lib/pkgconfig.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected .pc files:
    /usr/local/lib/pkgconfig/osxfuse.pc

The fix is:

cd /usr/local
tar -cvzf macfuse-backup.tar.gz \
    lib/libmacfuse_i32.2.dylib \
    lib/libmacfuse_i64.2.dylib \
    lib/libosxfuse_i32.2.dylib \
    lib/libosxfuse_i64.2.dylib \
    lib/libosxfuse_i32.la \
    lib/libosxfuse_i64.la \
    lib/pkgconfig/osxfuse.pc \

rm -f lib/libmacfuse_i32.2.dylib \
    lib/libmacfuse_i64.2.dylib \
    lib/libosxfuse_i32.2.dylib \
    lib/libosxfuse_i64.2.dylib \
    lib/libosxfuse_i32.la \
    lib/libosxfuse_i64.la \
    lib/pkgconfig/osxfuse.pc

brew prune

brew install fuse4x

This little snippet demonstrates nicely the idea, but it lacks important verifications, symlinks aren't copied over and the pkgconfig files aren't moved to the right subdir.
Fixed, tested on Yosemite the gist is here.
Thanx to Aaron, James and Yiufung . enjoy...