At least if you live in the USA.
Using the DMCA subpoena provision, RIAA managed to convince a Washington D.C. Judge that they should be allowed access to information about a Kazaa user identity from the users ISP Verizon Internet Service.
The Judge apparently believes that any copyright owner should be allowed access to any net users identity, just by the merits of alleged copyright violations.
Now, since this weblog is copyright protected — I should also be able to claim copyright violation from anyone downloading it without my written consent. So guys and girls, I am now on the way to Washington to get to know who you all are! ;-)