maxtorque: I think at least some of the analysis is also based on how hard it is to get to your password if a hacker gets hold of the hashed/encrypted version of it.
In the good ol days of NT passwords that Cougar mentioned you'd have L0phtCrack banging away trying dictionary and rainbow table attacks.
Something like "HORSE" would be found almost instantly as it is a simple dictionary word, "HOR5E" would be found seconds later as it is a standard letter substitution.
Edit: as Cougar has explained while I was typing..