http://forums.mtbr.com/29er-bikes/damaged-29er-xtc-composite-821040.html

Well worth a read…

What’s interesting about it? Customer finds crack after an impact (possible one they were unaware of like the bike falling over in garage and landing on something with a corner or something), impacts seatstay near the “seam”, bosh, crack.

Customer is well aware there’s an impact, doesn’t go straight to dealer because of this, sends photos to Giant who say “er, yeah, that’s an impact. No chance, pal.”

It may be on a “seam” but it’s still an impact. Why should they warranty something that isn’t their fault? It’d presumably be an impact sharp enough to dent an aluminium frame so I don’t see the carbon as an issue.