What Exactly Is a Domestic Partnership?

From the Gainesville Sun:

University of Florida employees have to pledge that they're having sex with their domestic partners before qualifying for benefits under a new health care plan at the university.

The partners of homosexual and heterosexual employees are eligible for coverage under UF's plan, which will take effect in February. The enrollment process began this month, and some employees have expressed concern about an affidavit that requires a pledge of sexual activity. . . .

In addition to declaring joint financial obligations, prospective enrollees must "have been in a non-platonic relationship for the preceding 12 months," according to the affidavit.

As a 29-year-old male, I think I'm obligated to make a crack to the effect of, "Hey, a lot of married people haven't been in a 'non-platonic relationship for the preceding 12 months.' Whoa!"

Seriously though, while I think that employers should offer domestic partner benefits, I'm not sure how to describe what constitutes a "domestic partnership." No employer wants to invest in benefits for roommates, but what makes someone "more than a roommate." If more states would offer civil unions for homosexual (and possibly some heterosexual) couples, this distinction would be a lot less confusing.

Specification: (Since Narnia is so en vogue right now) C.S. Lewis's relationship with Janie Moore would be a good candidate for a heterosexual non-marriage civil union. They were not related by blood and were not romantically involved, but they were nonetheless family.