Από το Μεγάλο Λεξικό (Εκδόσεις Οδυσσέας" - under "tail, 1":

We can't have the tail wagging the dog = Δεν μπορούν να διευθύνουν οι κατώτεροι τη δουλειά.

"Cutting off the nose to spite the face" is an expression used to describe a needlessly self-destructive over-reaction to a problem: "Don't cut off your nose to spite your face" is a warning against acting out of pique, or against pursuing revenge in a way that would damage oneself more than the source of one's anger.

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Note added at 5 hrs (2010-08-15 16:33:37 GMT)
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Also some interesting info on "tail wagging the dog"

Etymology: http://www.phrases.org.uk/meanings/341850.html

The earliest citation that I can find is from The Daily Republican, April 1872:

"Calling to mind Lord Dundreary's conundrum, the Baltimore American thinks that for the Cincinnati Convention to control the Democratic party would be the tail wagging the dog."

Dundreary is a character of Tom Taylor's play Our American Cousin. He was an amiable but dim nobleman, who frequently coined nonsensical riddles and twisted metaphors. These 'Dundrearyisms' were similar to Malapropisms and were briefly in vogue amongst US theatre-going circles in the 1850s. For example, 'a stitch in time never boils', 'better late than sorry'.

That Dundreary association leads nicely on to a witticism made by S. J. Perelman, the US humorist. He twisted the phrase after reporting his escape from the attentions of a group of prostitutes - 'It was a case of the tail dogging the wag'.

Evolution: http://www.metaphordogs.org/Dogs/entries/tailwagg.html

This phrase entered the legal lexicon in 1986 with McMillan v. Pennsylvania, a significant case regarding sentencing statutes. In the majority opinion then Associate Justice of the Supreme Court William Rehnquist wrote, “The statute gives no impression of having been tailored to permit the visible possession finding to be a tail which wags the dog of the substantive offense.” In so saying the Court “seemed to warn against a statutory scheme in which the enhancement is far greater than the underlying punishment.”reference 4 In other words, McMillan held that sentencing guidelines which call for extensions of prison terms based on aggravating factors cannot result in an extension longer than the sentence for the original crime. Are you with me? For instance, a tagger might get six months at most for spray painting a wall, even if she is a repeat offender; the sentencing judge cannot add six years because she has determined that the graffiti constituted (sentence enhancing) hate speech unless, and only if, the jury previously concluded that the content was in fact hate speech. The concept and what is now referred to as “the canine metaphor” were solidified in Blakely v. Washington in 2004 and US v. Booker in 2005.reference 5 In announcing the opinion in Blakely, its author, Antonin Scalia, declares without equivocation, though with a bit of a hitch in his voice, “The tail cannot wag the dog."