It's surprising i haven't seen a topic about this, but a while ago I got a mail from icepack stating that everyone who participates in clan wars gets a clan achievement, no matter if they wn or lose.
I'm personally not happy with this because it gives nothing to the winners.
I'm fine with a separate achievement, but if you give winners and losers the same achievement you're only harming the winners. Not only future winners, but also all previous winners. Because everyone who has ever won a clan achievement in the past will had a much harder time earning those achievements than people in the future. The achievements they have fought hard for with their clan will now become absolutely worthless.