WhiteElk: We have the tech and know how to support many more people than we got now. And i favor the voluntary birth control methods versus the heinous. The system must change.. but then it must anyway. If we don't do it, then it will be done to us. And that will hurt.
You know many of the "we can support many more people than we currently do" theories basically say that we can, but also involve using large amounts of resources to get there and also involve intensifying and extending farming practices (ergo vastly increasing the reduction of wild habitats)
In short yeah we can support many more people, but not without a cost. The cost is a far more rapid depletion of limited resources as well as depletion of resources beyond their ability to restore - as well as loss of ecosystems.
That said a great many poverty stricken countries could have significantly more food if stores and surplus from developed nations was more effectively shipped to them (instead much of it just goes to waste and ruin).
My view is population control will become something we have to pay attention to. If you don't you generally get one of a few reactions:
1) war - always good at lowering populations
2) disease - always a good natural balance as well to an overly populated species
3) increase in forced population control methods (China is a great example of where this became a needed policy).
Increasing education in family planning and contraceptive methods; increasing the validity of women in the workplace (ergo changing their social role to include more than just child production and raising); increasing the availability of contraceptives; removing social and religious barriers to family planning methods etc... are all great ways to naturally allow the social structure to lean toward a reduction in populations (heck it already happens at a very slow rate with many western peoples - its balanced out somewhat in those countries though by a higher influx of migrants).