gambolice is right, I am sure that there are scammers (those who do or used to to album scams and sell for real money) looking for good accounts to steal or good cards to steal (in addition to the type of situation that Kuro had, where someone just wanted to ruin his/her account for spite)
But some stealers may have good looking accounts and some may be very persuasive and build up trust over time, just like they do/did with album scamming.
We can probably never talk people out of piloting, even though it is obviously extremely high risk no matter who you turn your password over to (plus, to me, it seems kind of like cheating) but I hope Kuro's willingness to share this experience will at least remind people to, at a bare minimum, take a look at the wanna-be-pilot's account and don't hand over your password to someone who is under player level 100, low album count, low chapter progress, hasn't done many battles, has never ranked.. basically an account that does not look like a main or serious account.