The service is a market intermediary for extramarital affairs. Its founder claims that, by lowering search costs for affairs, he enables people in unhappy marriages to stay married. Daum says that perhaps she hears sounds of divorce lawyers lowering their fees, since they recognize that the divorce market is related to the market for extramarital sex.
The real question is whether providing low-cost flings increases or decreases divorce — whether making alternatives more readily available increases movement out of marriage.
I believe that this is unlikely; in a variety of contexts — including jobs, locations, and marriages — mobility is a push, with the pull from alternatives having little impact. So maybe the guy really is increasing well-being by lowering search costs, with no negative side effects.