dangerously low birth rate will be the biggest impact in long-long term - i wont be surprised if every other men uses this technique secretively to NOT to have a child ... as someone mentioned here "A SEXUAL REVOLUTION" is underway ...
We already have a 'dangerously low birthrate' in the US (and in many other countries from France to Singapore). By this I mean a working-age population too low to support the retirement costs of the preceding generation. Practically speaking, however, this can be offset by immigration and the demographics should have smoothed themselves out by around 2030 or so.
i won't be surprised if eventually small demographic countries banning this procedure :-)