I race and can beat most truggy drivers (not pro's yet, getting closer though) let alone most every MT driver I've run accross. I use to race my e-revo weekly, until I converted an 8t now I run w/ that most of the time, but I ran my e-revo for over a year though racing and beating most w/o a single diff issue, and let me tell you I have put my fair share of punishment on my truck. Here is the thing, if you drive it stupid, expect parts like that to break, standing back flips landing jumps WOT on concrete and asphalt etc.. expect serious damage to your drive line including the diffs. I'd expect about 99% of folk who have diff issues do those activities OR don't know how to adjust a slipper or think they can just set it and forget it w/ a diff, they need to be cleaned and oils swapped bearing checks at least a few times per year if not more. Bad bearings etc also another leading cause to early death of diffs. The early revo diff's were a touch weaker and may have issues but if you are running the e-revo diff's there is no 'real' problem.
PS not diss'in the alum diff's but you can buy a PILE of stock diffs off ebay for the price of one of them... LOL.
Here is a really old clip from ages ago too.. last year a few months after I started racing....
http://www.youtube.com/watch?v=vP4l4QEMB2Y