A few weeks ago I was reading an article on form UI by Luke Wroblewski of Yahoo!. For those who aren’t familiar with Luke, he (quite literally) wrote the book on good form design.
In the article, one certain section about placing labels inside of form fields stood out to me:
Because labels within fields need to go away when people are entering their answer into an input field, the context for the answer is gone. So if you suddenly forget what question you’re answering, tough luck—the label is nowhere to be found. As such, labels within inputs aren’t a good solution for long or even medium-length forms. When you’re done filling in the form, all the labels are gone! That makes it a bit hard to go back and check your answers. Luke Wroblewski
He brings up a good point. Generally speaking, you can look at a field that says “Tim Wright” and know that it was a field for your (my) name. But for long forms, yea, I do agree that you can forget some of the questions you answered.