In the context of network and internetwork operations, out-of-band means communications which bypass the normal structures put in place for such things; call centers, phone trees, and the like, and connect the people on the pointy end of the sword to one another directly.
They can be problematic for several reasons, if they're not used with some thought and care, but conversely, they can often seriously accelerate the speed at which problems get fixed. Finding the proper balance, as with so many things, is necessary to allow you to make best use of them.
- Baylink says: I'm pretty sure that this is because out-of-band communications are almost always between two people (note: not 'persons' :-) who know one another; this serves as an excellent lubricant for getting things accomplished.
A case-in-point example is the NANOG mailing list, which is often used for this purpose not because it *exists* to be a communications channel between employees of different networking organization, but because the members of that list know that many different such people are *reading*, and therefore it's a fairly target rich environment for such requests. As long as the noise from such things does not rise too high; it has in the past been fairly tolerated.