In my opinion, the motto, "Don't ask, don't tell", is not a very great one to live by. This motto can be applied in several situations, but I will give one example-- a relationship. If a man chooses to live by that standard motto, he may believe that it is okay to cheat on his girlfriend with other women. By his logic, if she does not know about the affair, it is okay. "Don't ask, don't tell" should never be used as a great way of logic.
Don't Ask, Don't Tell (DADT) was intended as a band-aid policy. The Clinton administration was ready to open up the US military to homosexuals, but there was significant push-back from the Joint Chiefs of Staff. DADT was intended to be a way for homosexuals to enlist while not outing themselves. Unfortunately, it still sent the message that homosexuals were not welcome. It was a step in the right direction, but it was still a demeaning policy.
I believe "Don't Ask, Don't Tell," is bad. It tells people that they should hide their true self and that is unhealthy for society and unhealthy for the individual. People need to be assured that it is okay to be themselves, they shouldn't need to feel that they have to conform.
Nobody owns your identity, and nobody should have to distrust his or her fellow soldiers. People need to be comfortable enough to realize that just because a gay person is serving with you doesn't mean they are going to sexually assault you, come onto you, or indeed even be remotely attracted to you. They need to trust each other and be comfortable with each other.