Bitcoin is starting to pressure these digital currency exchanges.  

Where they used to get 6%, or 8% to convert funds, they instead are now facing competitors like AurumXChange, which takes a minimal fee (1% for LR --> Mt. Gox,  2.5% for Mt. Gox --> LR).    So some of them turn to running scams (or increase the level of scamming they perform).

If they only scam the larger transactions, they can keep their long confidence game going (by processing successfully the smaller transactions, which gives the customers confidence to continue using the service except with larger transactions.  That works until one day, bam! Scammed.)