Good stuff here.http://www.geir.com/mythbuster.html
Pull tests on friction hitches for sling/webbing at Misty Mountain. The highlight with the yellow smiley face is scary. Also, a review of the test results indicate erratic and inconsistent behavior of the hitch/material interface.
Full report here http://www.docstoc.com/docs/115249971/MMT-Testing
19 Pull test Kelmhiest 1/2" Nylon Runner No slippage at 650 6 wrap
(10.5mm Dynamic Rope) 1/2" Nylon Runner No slippage at 460 6 wrap
1/2" Nylon Runner 2020 slippage at 1850 6 wrap
1/2" Nylon Runner No slippage at 1170 6 wrap
1/2" Spectra Runner No slippage at 1330 6 wrap
1/2" Spectra Runner No slippage at 610 6 wrap
1/2" Spectra Runner No slippage at 1180 6 wrap
1/2" Spectra Runner No slippage at 750 6 wrap
A colleague on mine in NC pulled the nylon and dyneema slings after the friction hitch tests, and the dyneema failed at a substantially lower loads than the nylon.
The bottom line: It might be better to have some nylon slings on your harness as well. I always carry at least one. It certainly can't hurt.
More interesting info here. http://www.mountainproject.com/v/105876750
It is around John Sherman's incident, but some of the comments revolving around testing are interesting.
My intent is not to discredit DMAN (he's credible and we've even shared a rope at one point). It's to be sure that you, as a climber make your own informed decisions that are not based on generalizations. I find that DMM video to be eyeopening, and although the test is harsh, and would be difficult to recreate on the cliff, it's not impossible. I try to stay objective and take the test data for the science it is.