Unwed young mothers the "new normal"?

A recent study suggested that more than half of births to women under 30 occur outside of wedlock. The trend appears to transcend racial and ethnic distinctions, though not necessarily economic class differences. Click on this link to read a New York Times report (2-19-12) about the findings. Are there social consequences (beneficial, detrimental?) to the replacement of marriage with a less formal kind of relationship?