Yep...me too.
Just saw a thread about this over on goodandevo.net and came here to see if this was a known issue. Lo and behold, i have TWO cracks at my power button, one on each side, one crack at the bottom of the volume rocker, and one in between the charger and HDMI port. They're small, hairline cracks, but they are definitely occurring where the plastic frame moves between wider and narrower sections. I have no cracks in any location where the frame is at it's widest...only around where the buttons/ports are located.
I have a Zagg screen protector only, no case, and my phone has never been dropped. I baby this thing and I'm disappointed to see this apparent design flaw. I also have light leakage/screen separation below and to the left of my home button. I guess this is karma for going over a year with my Pre, having no hardware issues...it's catching up with a vengeance.