So the International Consortium of Investigative Journalists scored the largest leak in history, and they've got the names of thousands of people with off-shore bank accounts, many (or maybe all) of whom are tax evaders. They have more than names: they have emails detailing fraud; they have transactions; they have amounts; they have account numbers... they have all the things a prosecutor needs.
But the problem is that the International Consortium of Investigative Journalists doesn't want to let anyone see their info. They say that it's a journalistic principle, but I suspect it has more to do with hoarding valuable intellectual property. They can dole out this stuff little by little in all sorts of stories and make a mint.
The Canadian government is apoplectic, arguing (reasonably) that there is a law on the books that any Canadian with knowledge of tax evasion over $100,000 must report the info to Canada Revenue Agency. The CBC (the sole Canadian member of the International Consortium of Investigative Journalists) is standing firm.
It's got to be the case that the US government is similarly desperate to get its hands on all those details. The irony is that if WikiLeaks had the info, they would make it all public. WikiLeaks doesn't hoard info so that it can enrich itself by dribbling out tidbits. WikiLeaks works for the public good.
...which is just why the US government is engaged in such a malicious attempt to wipe WikiLeaks out.