Just my two cents worth -- a 12 foot table doesn't really mean that you have a full 144 inches of quilting space. The machine itself eats up about 6 to eight inches of width and you have to allow that for both sides of the table, since the machine slides from one end to the other. You also have to allow for 3 to 4 inches on either side for clamping (if you use clamps). So about eighteen to twenty inches of table space has to be allocated to "administrative" space that can't be used as quilting space. So the absolute most quilting space that can be efficiently used is about 120 to 124 inches across the width, if the quilt is perfectly square, which is not common. Not because of poor piecing, but because that is just the nature of quilting. I hope this explains a little about why a 12 foot table cannot accomodate a 12 foot quilt top.
You can all hit me with a bat, but I have to say this -- I genuinely sympathize with the quilter who did not get her quilt fully quilted and was charged more (I truly cringe when I think of how unfairly and how poorly she was treated and I am embarrassed for the longarmer who did this) for the longarmmer's shoddy work. It should have never happened.