...I only trade for/buy ones that I like. Don't look to complete any sets or look for rare, valuable pins. But if I like it, it goes on my Disney World hat or on my lanyard.
I'm the same way.
My eldest started it in our family about 7 years ago. He bought his own pins and started trading. The next family trip, my younger son indicated he was interested, so I bought him a couple and he had fun. But then I saw the inherent "souvenir" aspect, and bought each child a "year" pin - the dated kind to commemorate their visit. By the next trip, I found the lots for sale on eBay, and that was it. All 5 of us got in to it, and pin trading became very much a part of our trips. Prior to the trips I would buy lots of however many in order so that we could go into the trip with traders, and then every trip they came home with a dated year pin, that I would buy on-site, as both DW and I would tell them not to trade anything purchase on-site for $6-12 when we were buying intended traders for like 50cents to a dollar each on eBay. They usually buy one or two on-site to keep and not trade.
In 2008 I got us one of those zipper pin carry-bags, and each of us has a page where we put all of our keepers - and it is very, very full. We each have a lanyard for the traders that we take to the parks, though I hate to wear mine, so it usually goes into one of the pockets of my cargo shorts.
Sadly, my eldest announced in April for our most recent family trip that he's bored with it now, and really doesn't care about pins anymore. I still got him his traditional dated pin - this time is was a 2011 WDW 40 pin, but he still hasn't even taken it off the cardboard card and put it in to the carry-bag.
The one who started it all has now quit on me. (When I went to
Disneyland last week, I didn't even bring one home for him, as I did for my other son and my daughter... I usually bring them a pin from each trip of something they are currently "in" to - or one that they saw on a previous trip but didn't buy for whatever reason.)
Like Barry - I look for ones that catch my eye - or my interest. I do NOT like to buy sets, or try to collect sets. In fact, before our April trip, in the eBay lot, there actually was a complete set, but I kept the one I wanted, and divided up the set between the family for trading purposes... none of them wanted the others either. We each have a favorite character, or film, or attraction, or whatever that we try to collect various pins of - but not just anything and everything. I personally like to get one from each resort that I have stayed at... I'm close to having a complete "set" btw with 17 WDW resort pins and 3 DL resort pins in my collection (out of 22 and 3 possible) - though it does go against the prior comment about not collecting sets!