Your attribute experiences

[MikeD]

In what ways do you guys use user attributes? How many attributes do you use on your e-mail list, are they required to sign up on your list, how do you implement them? Do you include attributes for later advertising? Etc...

For example, on one of my websites, it is catered to a specific niche, so I ask for name, address, phone number, contractor license#, fields of work (checkboxes). Only the name/email is required. Asking for this additional information makes it easy in tracking down specific people as needed.