I'm looking at the angle of social interaction, where people
know each other, not about virtual identities. There are many
like-minded people out there who open such sites and these are like
blogrings, people who know each other in real life.
Who needs to prove the IPs if testimonies by dead men can convict a
man for murder and send him to the gallows in Singapore. Very
often, allegations and accusations are already more than 50% of the
case, especially if it is very beneficial to the enforcement and
enhancing the value of a particular law or penal code legislation,
not to mention national interest.
Although, I must say the above is conjecture and not meant to
insinuate anything.
The third option is that RIAS has distributed trojan horse
softwares that are disguised as songs, and when downloaded, it has
a backdoor function etc. Thus, from their legal standpoint, the act
of clicking on this labelled "file" is an act of illegal
downloading, still, I'm no expert on this but I think it is likely
that their actions in tracking down individuals may have certain
elements that put it near the edge of illegal hacking.