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.