I have a dual socket motherboard (LGA2011) with two Xigmatek Dark Knight II coolers on it. Since I have the square mounting, the heatsinks literally bolt to the socket (not through the motherboard).
I don't make a point of moving my system around much, but when I have to, I have to. I haven't noticed any problems yet. What probably helps is the complete lack of clearance between the side panel and the tips of the heatpipes (the clearance is about 1-2mm).
I used a Scythe Ninja for a long time as well, and never noticed an issue moving that system around.
There were a number of drop tests for heavy CPU coolers even using push pins. The coolers are very well secured, and even after several years, I've never noticed an issue with any of my motherboards. Even GPUs flex much more noticeably, but no issues there either.
For system builders that ship computers around, the systems will typically have a piece of foam that the buyer will need to remove before use. The foam gets cut around the CPU cooler and placed into the computer, and will prevent movement. For the couple of machines I've had to ship around, I don't use tower coolers period. I go with a small, bolt through cooler that will not move and will not have issues. Puget systems will do this for SPCR Edition builds.http://www.silentpcreview.com/article1322-page3.html
|Dual Intel Xeon E5-2620-Xigmatek SD1283 DK-II|Asus Z9PA-D8-HR-05 IFX|WD 250gb Velociraptor SATA3|16gb DDR3-1600 ECC RDIMM|WD Blue 640GB SATA2 x2|Logitech K750|Logitech Wireless Mouse|nVidia GTX660ti 2GB|Antec HCG-750|NZXT Source 210 Elite|M-Audio ProFire 2626|Art TubeOpto8 with Smooth Plate Tube Swap|Avid Artist Mix x2|
A 9500GT with 1GB of RAM is the most pointless thing since NASCAR.