According to a translation of a Japanese advertisement, the 360 version of Battlefield 3 is so huge, no single disc can contain it. Instead, you'll get two discs when the FPS combat game ships on October 25. Not exactly a surprise -- we've suspected a multiple disc release since we saw the first BF3 demo -- but the ad offers something just short of confirmation.
If I were a betting man, I'd guess Battlefield 3 is split into a disc for the single-player campaign and a disc for the multiplayer, but instead of baseless speculation, I put a call into EA, and I'm waiting to hear back. When/if they confirm or deny the double-disc and offer details, I'll update this post and let you know, I promise.