Pin trading is awesome!

For kids and adults!
PROS:
1. You get to meet a lot of CM's!
2. CM's have to trade with you, if you have an official Disney pin and they do not have one like it on already.
3. There are special (green) lanyards for kids only, and they often have the coolest pins on them.
4. You can choose how/what you want to collect. Some people are ecclectic and have a little of everything, others pick a theme or series. I tend to collect Lilo & Stitch, Tink, and Pooh... my son does Pirates (all types), Nightmare Before Christmas, and Mickey!
5. Lanyards are cheap... ($5.00 and up in the parks) and you can sometimes theme them as well (like Pirates or Princesses, or the year of visit).
6. The lanyards full of pins make for the most awesome souvenier.
CONS:
1. It is very expensive. The cheapest pins in the park are $6.00. In one day last year I spent over $200.00 in the pin shop at MK on pins to trade!
2. Some people trade junk to the CM's (often buying it on Ebay) and even though you have a fortune invested, you in turn get junk.
Disneyshopping online sometimes has AWESOME deals on pins, try to check there weekly. They allow stacked codes, so when they run %'s off and free or reduced shipping, you can use them together!
Before Christmas I bought over 80 pins on there, all Disney pins, Limited Edition of 1,000 each, for a bit less than $2.50 each (including S&H)!

These are all for trading during our 2008 trip!
Use caution buying from Ebay, there have been many people that bought scrappers or untradeable pins on there!
Disney stores have genuine pins and I am told that sometimes you get great deals there as well!
If you go to the main WDW website and search "pin trading" it will take you to their official site, where you can download a guide. It is helpful!

It will specify exactly what is/what is not/and how!