Yep the Leicaphiles seem to be particularly paranoid about this - but they also believe there is an implicit magic in both the cameras and lenses (disclaimer: I do love my M4+Summicron). Speaking of which, I might have to crack open the Summicron as oil on the blades has migrated to the rear element and I'm not really into the whole diffusion effect. Any gotchas I should know about? As you can probably tell, there is zero documentation out there (only the chosen ones are allowed to fix these lenses).
Some people also just hear rhetoric like "NEVER TAKE APART A LEICA LENS!! THE PRECISION IS SO PRECISE AND THE SECOND IT COMES APART YOU'VE KNOCKED IT OUT OF WHACK!!!" and then just repeat it all over forums without having a clue what they're talking about. Well, I've taken apart nearly every lens I've ever owned and even some with built in shutters that weren't working and fixed them without a manual or anything. I've taken apart all my Leica lenses (28mm, 35mm, 50mm), some canon rangefinder ones for cleaning, etc. and they still take sharp and beautiful photographs.