I'm not so worried about taxes, rather about confiscation and more. Risks are potentially similar to running a Piratebay in the long term. Hausdorff is in serious trouble for running B24 in Germany. So not only does he have the Bitcoin mob after him (if the laws don't apply people get nasty quickly), the bank accounts were frozen in an instant, and he is charged with money laundering, financial terrorism, etc.
Singapore is one of the most strict regimes. If you look at organizations which are not liked, most countries obey to the US pretty quickly. Megaupload had some special forces come in, on behalf of Hollywood. So I think you need some serious cash for lawyers, and then a very smart strategy. A EU country is definitely not a good option.
Germany is a problem, considering that these are financial instruments with our law. It might be possible he needs a brokerage license to open the exchange and follow procedures after the german "Geldwäschegesetz" which is money laundering law. So it is technically absolutely legal to deal with this, however he did a few mistakes.
If he didn't follow the common ground rules, he is pretty fucked.
The first ground rule is not to withdraw company money in person. You wire it to yourself, to another account, that is designated personal. You keep money that is customer money ALWAYS in separate accounts and never withdraw cash from them (Red flag for banks).
The second is following AML law. Securing and identifying your customers is not optional. If you want to be a professional company, you need to follow the law.
As for megaupload: See what Schmitz did afterwards. I can't stand him, true. But he made the PRIME MINISTER of New Zealand apologize to him, he sued the FBI and got a court to show he actually cooperated and he is right now setting up new fibre cables for all of New Zealand just because he needs it for his service. THIS is how you deal with situations like these. But you need the money, that is true.