iTunes for Windows may attract hacks. What a surprise!
The bigger point is that all of these services are going to be under serious attack. The only reason they aren't is that they haven't tipped yet - but once they become a serious distribution channel, the race between hackers and security will be on. And if the services can't win it, their legitimacy (maybe even the legitimacy of digital music itself) will be under serious threat. Then the RIAA will go back to trying to extort CD's, and suing 'file-swappers'.