Confessing for someone else here, who may be on the forum but I'll not name names.
A little while back a friend of mine asks if I can have a look at her bike, install a new Headset and BB. No worries at all, being a Trek the Headset is just drop in bearings, and the BB press fit. Having had a few PF bikes I've had the tools for many years.
Anyway, my friend never gets back to me, following up I find out that while she was at another friend's place, that friend's dad overhears them talking and, having just received his new bearing press, wants to have a go...
So, the old BB is taken out with a hammer and screwdriver (thankfully the nice, shiny and light OCLV frame survives this abuse) and the new BB is pressed in accordingly...
Couple of weeks later I'm riding with said friend and I remark at the end of the ride how bloody loud her bike was and she agrees and also mentions its been shifting really shit.
Easy as, come over for a beer after the ride, check the bike on the stand and...
...
...
...
It's an oldy but a goody...
Needless to say the other friend was immediately notified about the fuckwittery and the dad swears blind he'd never do that but, that's the last time the chain was touched... The bike then got the mini overhaul, drivetrain check, new cable, new pads (metal on metal), quick bleed and all the other little things. Had to make a fair use of the beer payment and 20 mins work!