I always was against kernel spewing user-generated errors into dmesg, like this:
npviewer.bin: segfault at f6712030 ip 67e7a0 sp ff9c39ec error 4 in libpthread-2.8.so[677000+15000]
Not helpful, not interesting.
However, the other day my desktop keeled over in a strange way... The /var/log/messages contained this (followed by a stack trace):
Apr 13 18:19:14 niphredil kernel: Xorg: page allocation failure. order:3, mode:0x4020
It looks like a bug in SLUB (does not seem registering with anyone who has the power to track it down though). But my point is, without the printout I would need to find what was happening by other means, and that would probably take forever.
Hmm... My world is shaken.
P.S. kgdb was merged into 2.6.26. The sky is falling.