Do Most Restores Really Fail?

Every once in a while I see some analyst, usually talking about some backup to disk product, say "X% of all attempts to restore from tape fail" where X is some ridiculous number like 62.7. While I've been involved in my share of restore disasters from OnStream tapes and no OnStream drive to "We found tapes 1-3 and 5-8 do we really need tape 4 of that set" 95% were due to stupidity of some sort. So tell me folks what percentage of your restores fail? Good restore war stories also welcome.