Nami's breasts have been growing exponentially since One Piece began. She appeared on the first episode. This is her first appearance ever on the anime:

Okay, normal little girl... Now, we fast-forward into ep. 93:

As you can see, she's gained a few gallons. Also notice that her waist is much thinner.
Now for the final result:

One Piece, the Fanservice Movie.
What the hell? Look at the size of those things, how does she even stand up? x_X That's like a "D to the power of 7"-cup. Breasts like that are unnatural and should be destroyed.
The question here is why the hell did Oda feel the need to do this to her. Does he not get enough sex from the wife? Because fanservice attracts viewers? Is Nami on some kind of mammary-enhancing drug? Is it the effect of the crazy magnetic fields in the Grand Line? Are they two giant tumors? Did she eat a Devil Fruit when no one was looking?
Here's a little timetable as well:

Here's what other people have to say:
http://apforums.net/showthread.php?t=9362 (where I found the pictures)
http://groups.msn.com/OnePieceMangav-2/ ... e=0&CDir=2