I could see this as being a good strategy if you didn't declare it, but
   by eliminating vowels you reduce the search space.
   It's only a good tactic if people actually switching from using
   dictionary words to using something with higher entropy. More likely
   though, you'll start to see things like 'bbbddq' or 'cmplt sntnce,' and
   the users will still be susceptible to dictionary attacks.
   It's important to remember that a good dictionary attack has a
   dictionary that is much larger than a list of words in different
   languages, it also has common patterns. This sort of restraint probably
   reduces the usage of dictionary words but increases the usage of other
   common patterns.
   I don't like it.

   On Mon, Nov 11, 2013 at 7:29 AM, J.A. Terranson <[1]measl@mfn.org>
   wrote:

     Mildly interesting, for those who have an interest ?
     //Alif
     --
     Those who make peaceful change impossible,
     make violent revolution inevitable.
     An American Spring is coming:
     one way or another.
     ---------- Forwarded message ----------
     Date: Thu, 7 Nov 2013 14:01:15 -0500
     From: William Arbaugh <[2]warbaugh@gmail.com>
     To: [3]dailydave@lists.immunityinc.com
     Subject: [Dailydave] Don't use vowels in passwords!
     According to the Defense Finance and Accounting Service (DFAS), you
     shouldn't use vowels in your password!
     The DFAS web site [4]myinvoice.csd.disa.mil is instituting new
     password requirements starting tomorrow. The details can be found at
     the site (if you're willing to read a PDF hosted by DOD that is).
     DFAS brings us two significant improvements to password/PIN security
     by forbidding the use of vowels, and requiring that password/PINs be
     EXACTLY 15 characters long (no more, no less). I'd guess that the
     first requirement is to prevent people from using dictionary words.
     The second requirement is probably due to some obscure issue with
     their use of an Oracle Java front-end.
     This is from a web site that until recently ( and I believe still
     does) required the use of IE and Java 6. Logging in use to require
     clicking through no less than 3-4 security warning pop-ups.
     _______________________________________________
     Dailydave mailing list
     [5]Dailydave@lists.immunityinc.com
     [6]https://lists.immunityinc.com/mailman/listinfo/dailydave

References

   1. mailto:measl@mfn.org
   2. mailto:warbaugh@gmail.com
   3. mailto:dailydave@lists.immunityinc.com
   4. http://myinvoice.csd.disa.mil/
   5. mailto:Dailydave@lists.immunityinc.com
   6. https://lists.immunityinc.com/mailman/listinfo/dailydave