Some consider last week to have been a possible tipping point in the struggle over the definition of marriage in America. Gay advocates cheered Feb. 23 when the Obama Administration announced it would no longer go to court to defend the constitutionality of the Defense of Marriage Act. Though the decision did not immediately affect any part of American life except the way four cases — two in Massachusetts, one in New York and one in Connecticut — are being litigated, speculation about the long-term fallout is anybody’s guess. What is clear is that the president’s decision was rare and that it sent traditional marriage advocates scrambling for a response. Here are 10 areas of American life, or American institutions, where the struggle to define marriage is most notable.