As Valentine’s Day 2009 arrives, the desperate real-estate salesmen of Glengarry Glen Ross are an apt metaphor for the romantic plight of our age. Plenty of prospects out there — there are some 24 million women ages 18-29 in the United States — but guys can’t seem to close the deal: 65 percent of those women have never married. The median age at first marriage for women, which was 20 in 1960, is now at an all-time high of 25.3, and spinsterhood is an increasingly common fate. Thirteen percent of women 40-44 have never married, reflecting about a one-third rise since 1980 in the likelihood of being an old maid, a percentage that can be expected to increase given the current low marriage rates for young women. . . .