Bitcoin trading: security I have seen different trading websites on Bitcoin and a question came to my mind:

Security
Why do they require so much identity verification? If I remember correctly MtGox (despite what later happened) when it started, it didn't require any id\bank verification. So my question here is: is identity verification required by law even when dealing with bitcoin trading or is it an anti-fraud system enacted by the trading operator?
All services that deal also with fiat money, apart from cryptocurrencies, must comply with specific AML (Anti Money Laundering) and KYC (Know your customer) rules, which can be more strict depending on their jurisdiction. 

AML/KYC Explained: https://bitcointalk.org/index.php?topic=454795.0