[activepeanut]

http://en.wikipedia.org/wiki/Hanlon%27s_razor

  Never attribute to malice that which
  is adequately explained by stupidity.

[001sky]

The question is <whose> stupidity? Assuming "the customer is always right", that leaves the vendor.

Although you may be implying: "the customer is always stupid".

[Knacker_Hughes]

Malice and stupidity aren't mutually exclusive.