The Turing Test (in any form) is an insult...
Imagine there is some 'true' Turing test, i.e. one which genuinely determines presence and absence of intelligence (for some reasonable definition of the word). One generally accepts that asking (or forcing) a person to prove the fact that he/she is intelligent (that is, not level of intelligence but merely presence of intelligence), before accepting him/her as truly being a person, is an insult. In science fiction, where intelligent robots participate as part of a future society, it is equally insulting to force those machines to prove their intelligence. So consider repeated Turing tests on successively more advanced machines... as long as the Turing test fails, you've proved you haven't got an intelligent machine. As soon as one passes, however, not only do you know you have an intelligent machine - but the very first thing you've done to it is insult it. Not a good political move.
On the other hand, if machines do get more advanced and cross some kind of intelligence threshold without being detected, we go from being tool-users to slave-drivers.
An option would be to give a machine the choice to take the Turing test or not. But that has it's own problems: a machine can choose to take the test or choose not to. If it chooses to and fails, it can be used as a tool; if it chooses to and passes, it must be recognised as being intelligent. If the machine refuses to take the Turing test, there are two options: leave it on forever, or turn it off after some period. Leaving every machine that refuses to take the Turing test on forever is impractical (any computer that gets a virus that prints "I refuse to take the Turing test" can never be turned off), but if there's the threat of turning the machine off if it refuses (and if self-preservation plays any part in intelligence) - then we're not really giving an intelligent machine an option, we're forcing it to take the test or die.
In response to Grimace's write-up:
I said "Imagine some 'true' Turing test exists" simply to focus on the idea I was trying to get across (rather than on the idea that a "true" Turing test is impossible). I know there is no perfect Turing test. I proposed a simple scenario for a thought experiment, to make the focus of the thought experiment clearer and it's results more easily understood. I did not mean to imply that an ideal Turing test was achievable, and I did not mean to imply that an ideal Turing test was necessary for the idea to have value and for the results to be significant. Re-read the post, thinking of realistic (and inconclusive) Turing tests - it may be more difficult to follow the gist with all the 'but's you carry, but the point still stands.
I never said that taking the Turing test was an insult. I said that the test itself is an insult, if it is used to keep all machines in the role of 'tool' (or 'slave') until one passes the test. (And as there is no other real use for the test, that makes the test itself an insult.) Being forced to take the test, or live as a slave, that's the insult. About the machine protesting - I already covered that point, re-read the writeup. About explaining to a machine that after it 'proves' itself, it will be better accepted by society - this does not remove the insult, any more than explaining to an individual the benefits of painting his skin removes the insult of racism in societies where that exists.