A couple that we know has recently announced their decision not to have children, based on their observations of friends who do have children - they've considered it at length and decided that neither of them is prepared to put their careers at risk / on hold, that they like their life as it is, and that they're not prepared to undergo the lifestyle changes that they've seen us (and other friends) undergo.
Some other close friends of ours are now reaching the same point - they've seen how much having a child impacts on your lifestyle, in terms of flexibility to do what you want, when you want (I hasten to add that we haven't been moaning to them about parenthood - just that they've been observing keenly).
Anyone else have a similar story?