Funny you should ask because I had the exact same concern coming home from WDW in October.
I asked a security person at the airport what the rule was before checking our bags (in case I had to do a little re-packing of my 100 pins LOL). He stepped away, consulted with a co-worker, read something and returned to inform me of a rule that is in their official guide that I found humorous.
Seems there is an official policy addressing the wearing or transporting of "excessive amounts" of lapel-style pins. They are permitted in carry-on luggage when traveling to or from Orlando or Southern California airports.
I thought it was very entertaining that a Disney activity has caused the need for its own national air travel security rule.
- Dreams