Temporary suspension of HSBC Deposits
I suspect that at least some of this drop was caused by Mt Gox having bank issues in Hong Kong.
Exactly what kind of issues?
posted this on Mar 13 12:08
Dear Mt.Gox users,
This is a notice to inform you that we have temporally removed our HSBC deposit option from MtGox.com. We have noticed that many recent deposits to this account appear to be fraudulent, so we are being cautious while we investigate.
Althought HSBC deposits are currently suspended, all withdrawals from HSBC are currently routing without disruption. For the time being we invite our international customers to make deposits via our Japanese SMBC account and to avoid sending to our HSBC account.
Finally, we believe that we will be able to resume all deposits to our Hong Kong HSBC account at a maximum of two weeks.
The Mt.Gox TeamOtoh's post edit: this same info can also be found on Gox's International wire deposit page