Personally i think that if you're actually concerned about losing a few precious bottles, be they glass or PET, then you're really not understanding the whole purpose of a case swap. We are there to sample other people's beer, not sample their bloody bottle stocks you whinging idiots.
Let me spell it out for you all
1. MAKE BEER
2. BOTTLE BEER IN BOTTLES OF ANY TYPE
3. BRING TO CASE SWAP
4. ENJOY
it's really not that hard. Anyone who doesn't want to participate because they're afraid of losing their precious glass/PET tallies can stay at home I reckon. Just be happy that a bunch of like-minded people can get together and share their passion.
/rant off