I am a first-generation immigrant who married an American. I live in the greater Miami area. This part of the country is very Latin. You can find the largest populations of Cubans, Venezuelans, Argentinians, Colombians, and Brazilians in the United States, in addition to many more.
And the unwritten secret is - if you come from Latin America and want to stay in the United States-- find a Cuban to marry. I know at least 10 individuals (not couples) who have "fake" married to get a green card.
Then, there is the case of Hope Hall, a US military veteran, as reported in Reason.com:
Hope Hall, an American citizen and military veteran, and her Canadian partner and soon-to-be wife Nathalie Gaulthier, who runs an internationally renowned circus arts school and has spent 17 years living and working in the U.S. Though marriage is often the one reliable path to citizenship for many straight couples, the Defense of Marriage Act prohibits United States Immigration and Citizenship Services from granting the same legal rights to gay couples, even those married in a state where gay marriage is legal.
So, my question to you is, wouldn't it make more sense to allow all adult citizens to just sponsor a limited number of people for American citizenship?