HNK found a reference in the Chicago city code that bars het dating services. As posted to craigslist:
No person shall advertise… to act as agent, go-between… between a man and a woman, for any fee… for the purpose of promoting a marriage or an acquaintanceship intended to result in marriage.
Heck, that’s even what the Lincoln Park Trixie Society is about! The fine’s $100-$200, and another part of the same law specifically states “a man and a woman.” Yay, gay people!