Just read the article "Hadoop brings far-flung people together across time and space"
eHarmony is a 13+ years old obsolete site using Big Five traits to measure personality of its members, and Big Five normative personality test is only good for informative/guidance purposes but not good enough for predictive purposes. Many Psychologists began to use the HEXACO model of personality during 2013 to replace the Big Five test, but I suggest to use the 16PF5 test.
Worldwide there are over 5,000 online dating sites, no one uses the 16PF5, no one is scientifically proven yet, and no one can show you compatibility distribution curves, i.e. if you are a man seeking women, to show how compatible you are with a 20,000,000 women database, and to select a bunch of 100 women from 20,000,000 women database.
eHarmony's algorithm is in the range of showing you 3 most compatible persons per 1,000 persons screened, and with the 16PF5 you can reach 3 most compatible persons per 100,000 persons screened; a 100 times more powerful algorithm (NOT 100% improvement, a 100 X improvement, really an innovation)