Homebrew: SHA1 Mismatch Even After Update
If you're certain the downloaded tarball for sshfs is good can try to force Homebrew to install it with:

brew install -f sshfs


More than likely though, if it still complains, is you've got a corrupt tarball download. You can remove /usr/local/Cellar/sshfs/2.4.0/sshfs_2_4_0, which is the cached tarball that Homebrew downloaded, and have Homebrew try downloading the package anew.

If it still complains about the hash value mismatch, you can edit the recipe and update the MD5 checksum for the file in the recipe and then install. The file to edit is /usr/local/Library/Formula/sshfs.rb. Looking at:

/Users/ian/code/tmp/brew [ian@Ian-Chesals-MacBook-Pro] [13:13]
&gt; cat /usr/local/Library/Formula/sshfs.rb
require 'formula'

class Sshfs &lt; Formula
  homepage 'http://fuse.sourceforge.net/sshfs.html'
  url 'https://github.com/fuse4x/sshfs/tarball/sshfs_2_4_0'
  md5 'c9ea547b9684ec4d85437393a2731322'
  version '2.4.0'

  depends_on :automake
  depends_on :libtool

  depends_on 'pkg-config' =&gt; :build
  depends_on 'fuse4x'
  depends_on 'glib'

  def install
    system "autoreconf", "--force", "--install"
    system "./configure", "--disable-debug", "--disable-dependency-tracking",
                          "--prefix=#{prefix}"
    system "make install"
  end

  def caveats; &lt;&lt;-EOS.undent
    Make sure to follow the directions given by `brew info fuse4x-kext`
    before trying to use a FUSE-based filesystem.
    EOS
  end
end


You can see that you need to download https://github.com/fuse4x/sshfs/tarball/sshfs_2_4_0 and recalculate the MD5 checksum for the file and then update the recipe. So:

/Users/ian/code/tmp/brew [ian@Ian-Cs-MacBook-Pro] [13:13]
&gt; wget https://github.com/fuse4x/sshfs/tarball/sshfs_2_4_0
--2012-07-23 13:13:53--  https://github.com/fuse4x/sshfs/tarball/sshfs_2_4_0
Resolving github.com... 207.97.227.239
Connecting to github.com|207.97.227.239|:443... connected.
HTTP request sent, awaiting response... 302 Found
Location: https://nodeload.github.com/fuse4x/sshfs/tarball/sshfs_2_4_0 [following]
--2012-07-23 13:13:53--  https://nodeload.github.com/fuse4x/sshfs/tarball/sshfs_2_4_0
Resolving nodeload.github.com... 207.97.227.252
Connecting to nodeload.github.com|207.97.227.252|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 52812 (52K) [application/octet-stream]
Saving to: `sshfs_2_4_0'

100%[===========================================================================================&gt;] 52,812       288K/s   in 0.2s    

2012-07-23 13:13:54 (288 KB/s) - `sshfs_2_4_0' saved [52812/52812]


/Users/ian/code/tmp/brew [ian@Ian-Cs-MacBook-Pro] [13:13]
&gt; md5 sshfs_2_4_0 
MD5 (sshfs_2_4_0) = c9ea547b9684ec4d85437393a2731322


In my case the computed value for the download matches the value in the recipe. If it's different for your case it's likely your download is corrupt. You can go ahead and update the recipe if you think your download is not corrupt.

Note: I did a brew update before running the above so I can attest to the fact that I do have the latest recipe for sshfs and that the MD5 checksum for the tarball in the recipe is correct and matches what gets downloaded from github.

Caveat Utilitor if you do this.