First of all, I can appreciate how there is confusion over this point. Figure 8-2 in the manual shows a similar bumper configuration, however the Q&A points out that figure 8-2 is not necessarily an example of a legal configuration.
http://forums.usfirst.org/showthread.php?t=11257
In this case the corner will likely need to be protected by bumper material on both sides of the corner, and the shortest allowable piece of bumper is 6".
http://forums.usfirst.org/showthread.php?t=11218
I can totally understand how teams might have designed their robot in keeping with figure 8-2 prior to the publication of these Q&A responses and assumed that because it was shown in the manual and seemed to be consistant with the intent of the bumper rules (that the first thing to hit a wall or robot is always a bumper) that this configuration of bumper would be legal. Indeed, the GDC, through Q&A and team updates may clarify that this is an acceptable configuration. Based on my reading of the rules as they now stand, however, this is an external corner of the robot that is not protected by bumpers on each side of the corner, and thus is not a legal configuration.
Jason