I'm utterly shocked at some of the comments here, 'If you can afford it why not have as many as you want?' is a childish answer to a serious question, it's the equivalent of saying, 'well as long as you can afford more food, why not just keep eating! What harm can it do?' - well it can do a lot of harm, and seriously, so can churning out lots of kids.
Not in the short term, no, for us, we get all the benefits, lots of smiling faces, lots of love, lots of people who we cherish and care about, and lots of people who care about us too. Plus it helps satiate that biological tick!
However, we're setting up a ticking time bomb, not for our children, but for their children. In the next 10-20 years, we're going to find it hard to find jobs for all our young people - it's already tough. We're already seeing food prices rise - and yes, even chocolate is said to become as expensive as caviar by the year 2020. Although our wants and our ambitions are boundless, our resources aren't. Imagine two worlds
One where everyone has to temper their wants, but everyone has what they need. Everyone has homes, everyone has food, everyone has clothing and everyone is relatively safe.
Imagine the other where few if any have homes, food is in short supply, every day is a struggle for survival, crime is rife as employment is low.
You can choose which life you want your grandchildren to live. Don't take away the power you have to choose. Don't imagine that the problem is too big, and what difference will what you do make. Our children are the most precious thing we'll ever have, and we should put their welfare before everything, whether we're their to see it or not.
This sounds like I'm being inflammatory, but please, please, please, just for a second... think.