Population growth has some worrying trends if you start thinking in historical time frames. If we continue to grow as is, until we reach some sort of natural barrier we double the population ever 50-60 years. What will the world look like with 25bn (100yrs) or 100bn (200yrs)? What will it look like @ 1 trillion (say 300- 400 yrs)? Somehwere between 50 & 500 years from now we may know the limit. That's not that long in historical terms and it will probably be a recognizable world. Most of the same countries & cultures will probably still exist. Elvis might still be popular.

If growth does stop what will stop it? Culture (ie middle class western Europe) or something "natural" like famine?