I've filled it previously, sent them my id and bill and registration card. Then entered the bank data with swiftcode etc.
Now the ask for this:
We received your withdrawal request. As your withdrawal request met some of our volume and frequency thresholds, we will have to kindly ask you to help us better understand the nature of your relationship with Bitstamp. In order to do so, we require that an additional KYC (know your customer) procedure is completed before we can proceed with the processing of your transfer.
We kindly ask you to send us a high resolution image double page of your international passport and answer the following KYC questionnaire:
1. How did you learn about Bitcoin?
2. The purpose of trading on Bitstamp?
3. What is the origin of the deposited Bitcoins? If mining, please specify your hardware specifications and submit a receipt or an invoice for your mining equipment.
4. What are your future plans and activities planned on our exchange?
5. Do you plan more withdrawals in the future?
6. Which bank are you using? Please provide the complete address and SWIFT code.
We kindly ask you to submit your answers and documents in a reply to this ticket.
Assuming this is true, it's kind of weird, as it does not look remotely similar to KYC questionnaires handed out by traditional banks in the euro area. Of course some of the questions would have to be different, but a bank is not allowed to ask a customer where his/her funds come from. In some countries, tax authorities have the power to go through banking records and ask this very question even in the absence of a subpoena; what banks can do is transmit information on suspicious transfers to the proper government offices, but they are not directly interacting with the client on the matter of where the money comes from.
I would be more worried about malicious use of this data on the part of Bitstamp than anything.
The request about mining equipment specification baffles me entirely.