Oh and...it happens a lot more then you might think:

Gays being kicked out of military at steady rate
http://www.boston.com/news/politics/politicalintelligence/2009/05/gays_being_kick.html

http://www.logcabin.org/lcrchicago/gays_military.html :
"As of June, 2007, 58 linguists fluent in Arabic have been kicked out of the military for being gay. This happened even as intelligence agencies complained about a shortage of linguists fluent in Arabic, and the military itself is desperate for Arabic translators."

"Allowing openly gay service members will not hurt unit cohesion or competence. Our closest allies allow openly gay service members, including every member of NATO except Turkey. Research shows none of the countries with openly gay service members have been hurt by their non-discrimination policy. England, Australia, Canada, New Zealand and Israel are just some of the 24 nations that allow openly gay members in the military. Even South Africa allows openly gay service members.

Even though many opponents predicted problems in these countries before their bans were lifted, time proved them wrong. Researchers say not a single country with openly gay service members has reported any decrease in morale, recruitment, retention or cohesion."

"Furthermore, a 2006 Zogby International poll, commissioned by the Michael Palm Center, of U.S combat veterans from the Iraq and Afghanistan wars, found that 75% of were comfortable working with gays and lesbians, and 68% either knew for certain or suspected there homosexual members of their own unit. Yet clearly the combat readiness of our military has not suffered with the known presence of gay troops. "

"The Don't Ask, Don't Tell policy is corrupted by some people as a way of avoiding military service. Research shows, and even the military admits, that a sizable percentage of those kicked out of the armed forces for being homosexual are actually heterosexual. They use the policy like a get out of jail free card. Eliminating the policy would close this loophole."

"The military wastes millions of dollars each year investigating "violations" of the Don't Ask, Don't Tell policy. With a huge budget deficit, this money could be better spent on projects that actually improve national defense."

" The combination of personnel losses are far higher than the 600-750 people per year kicked out under DADT (#1 above). A 2007 analysis of retention data by Dr. Gary Gates of the Williams Institute at UCLA Law School, based on an academic survey of GLBT veterans, found that 19.2% admitted to voluntarily leaving the military because of the difficulties of serving under DADT. This translates to 3000-4000 people per year!! And it has been going on for 13 years. And every one of those 3000-4000 people are already paid for, trained and experienced. You simply can't replace them with a raw recruit off the street. "