no ones jumped on this?.....they are small metal tabs located on the rear brake pad on disc brakes...they are posistioned to begin rubbing on the disc just before the pad wears down to the mounting rivets which in turn will cut into the rotor(the mounting rivets that is)

 

Just to add to what TexfordD stated.

When the pads wear down far enough the wear indicators will rub against the disk causing a noise, sounds kind of bad. This is to let you know you need pads.

It is not going to hurt anything until the sound goes away, once they stop making the noise you could damage your disk real bad.