A couple of things come to mind...
In 2002 I bought a ZX-9R from a bloke who worked at MCN (that should have been sufficient warning in itself) - aside from it being absolutely minging beneath the fairing ("only rode it once in the winter"... my ar$e!) The crowning glory of his work on it had been after he'd had the wheels painted - when I removed the rear I noticed that the heads of all the brake disc mounting bolts were severely scored, and that the inside face of the rear caliper mount had some quite deep gouges in it. Initially I was quite worried that something was way out of line, until I removed the disc and found that the muppet had put it on back to front, ie with the counterbores on the mounting bolt holes on the inside, so instead of sitting within the disc and being nice and flush, the bolt heads had been proud of the disc and fouled the bracket really badly - it would have been impossible to turn the wheel by hand... and he hadn't noticed FFS! All he must have done was rev it up and dump the clutch and ride through it until the bolt heads had carved themselves some clearance through the aluminium of the caliper bracket... Anthony Orfeo, shame on you!
Another one is a Ducati Monster that an old girlfriend of mine owned, she bought if via ebay to go racing in the Desmo Due series, and her friendly local dealers helped her out quite a bit, including some "race prep" that I discovered when I serviced it for her a few months later...
It came to me like this...
and left like this...

"Racing is life. Anything before or after is just waiting"
Steve McQueen
Wheelies - they ARE big and they ARE clever