While deciding to exchange almost 350 SGD at an "Authorised money exchange", the ones which have a relatively higher exchange rate than what you get at the K-Mart exchange rates. It was on the way to Ku De Ta and there was a cute dog outside (which was a distraction for unsuspecting tourists, realized later). The guy offered a rate of 9100 for 1 SGD (the airport was giving 8600).
Now, the trick is, these guys separate the Rupiah into piles and make ou count each pile separately, When they are sure you are satisfied with the pile, they collect the money together and while collecting, they "DROP" almost 30% of the notes into their desk below. It's almost like a magic trik, so if you miss it, you would think he has just collected all the money. With Indonesia's weak currency and large number of notes, it's easy to not realise that a large chunk of notes are missing. You lose almost SGD 100 worth of Rupiah and realised it only 3 hours later, when one had to exchange some more money and one SAW this other guy DROP a bunch of notes from the pile while exchanging the money.
Please DO NOT fall for this scam. Always count the money when it's in your hand, and before leaving the shop. Better yet, please go for the airport like rate, and get a receipt!