The only real dynamic reason for spacers is to stop wheels rubbing on big brakes/suspension struts. The main reason they are used though is to make cars look better, but this doesnt mean that your car is going to explode when you fit them.
josh - the post showing the GTR is incredibly rare and unusual, it certainly shouldnt happen when using any kind of decent quality spacer anyway. The forces that would be involved to do that on a 5mm spacer as you are talking about are incalculable, the physics just wont let it happen. Youre in the clear mate
To add to that -what I said above and what you have queried relates to warped discs caused by poor quality slip spacers (3mm added to good quality 20mm spacers in my case) that simply 'squashed' in places that led to the spacers not running true with the discs and hence the warping.
As said above, if use good quality spacers there should be no issues. I went to a drift meet on Sunday and you ought to see the size spacers some of those guys are running 60mm+ and given the forces they are put too it more often that not it is the drive shafts that fail but then with 1000whp+ going through the hubs from locked diffs in some cases ...........