I came across a very interesting psd file today. http://dl.dropbox.com/u/56753740/tag-cloud.psd (original source http://www.premiumpixels.com/)
The file contains a lot of tags with different widths all created from the same smart object. The interesting part is that "the small design with the hole on the left of each smart object" remains in perfect proportion while the width of the entire smart object has been changed.
If I select a particular tag ans press ctrl+t, the smart object immediately changes to it's original size and any re-sizing will result in distorting the proportion.
If I go inside the smart object and make any change and update it, the entire tags will revert to its original size.
What I want to know is, How do you resize a smart object keeping aspect ratio of only certain elements within the smart object intact? As you can see the same is being done in the attached file. This'll give me tremendous advantage while designing buttons of different sizes and being able to control the design from within only one smart object.