As soon as I read this I thought of something right away - the trunk wiring harness. E36s, E46s, E39s (including my own) have all had breakdown of the wiring in the rubber rube connecting the body to the trunk lid.
When I got my E90 I noticed this looked almost identical to the E39 harness but I was hoping they had updated materials or something.
My E39:
http://pics.uplink.ca/public/2007-01...9TrunkHarness/
Just one random Internet thread on the issue:
http://www.bimmerfest.com/forums/sho...d.php?t=397245
Don't be surprised if this affects E90 sedans too. Once or twice per year you'll need to pull that boot back and inspect or repair.