One day my account (solely used for sending payments) got blocked because of a "potential unauthorized third-party access". After completing the verification they asked (new password, new security question and credit card confirmation), I received another message asking me to send a scanned copy of my ID Card, a proof of domicile and my BBAN.
I told them that for confidentiality reasons, it was out of question to send any of these documents. I asked them to give me more specific information about the materials that led to the account suspension and to reactivate it without delay. The next day, I received an email with vague excuses and my account got reactivated immediately.
It is true that their antifraud system can lead to number of suspended accounts and frozen funds without any solid basis. But they may also take advantage of frozen money (eg. this 600k case) for further financial activities so as big-box stores are used to: http://books.google.com/?id=UOSk0J8vYugC&pg=PA533 (source: http://preview.tinyurl.com/2vrcddc)