The annoying ones are those cases where there's a known fault, but the dealers close ranks and all say "first I've heard of it". Case in point, my Dad had a 2002 Renault Laguna as a company car. Great machine when new, went like a rocket, only snag was that after a few months it started throwing up spurious fuel injection faults which put it into "limp home" mode until you pulled over, shut down and restarted. The local dealer gave the "first I've heard of it" line - really, in that case why was there a forty page topic of Laguna fuel injection/intercooler/turbo faults on one forum...
I strongly suspect that Renault knew very well what the problem was, but it would have put a serious dent in their profits if they'd admitted it and called all affected cars in for repair.