In the contentious debate over immigration policy, three groups have dominated public and political attention: the roughly 11 million undocumented immigrants seeking to become legal, the skilled foreign workers bound for high-tech jobs and relatives waiting to be reunited with their families.

Then there are those who won the green card lottery.

This tiny visa program, aimed at diversifying the pool of immigrants to the United States, selects 55,000 applicants at random each year. Unlike the other U.S. visa programs, it offers the "winners" and their spouses and children U.S. residency with almost no strings attached. Although the odds of winning are infinitesimal, the program is so wildly popular that last year almost 8 million people applied.