How does employment affect a mortgage?

So, an interesting question was posed today, "How does changing employers affect a mortgage?" I was curious, so I did a little research and even called my bank.
The simple answer, at least for me, would be that it wouldn't. For any normal person, as long as they're staying in basically the same line of work, changing jobs won't make a huge difference on their ability to qualify for a mortgage. Obviously, your lending institution might have different rules, but my bank said that all they would need would be 30 days worth of pay stubs, basically to prove how much money you're making.
For some people, changing jobs can have a disastrous impact on the qualification process though. If your income is based off commissions, or a lot of your income is based off bonuses, it might be a good idea to put off changing jobs until after you purchase your new home. It is also recommended to put of becoming self-employed or changing jobs if you only work part time.
The reasons for this is the way lenders calculate your income. For the most part, they like to average your income for the past two years, and if your income varies from month-to-month in your new job, they won't have as much data to make their calculations and it may look bad.