Any opinions on whether it's safe to backup pirated stuff online (places like CrashPlan, Carbonite, etc)?
Not sure about backing up the files and how they'll be handled, if discovered. There probably isn't that much risk in doing so, but just to be safe, packing everything up in something like a Truecrypt container seems like a good idea.
CrashPlan and Backblaze both have the option to encrypt the archives online using a local password. Haven't used Carbonite. While there's certainly no absolute guarantee they aren't logging this password somewhere, they claim they aren't and are very clear that the loss of the password is going to make your data unrecoverable. Given this claim, I'd say they'd have a pretty hard time going back and saying, "ha ha, remember how we said we didn't log this? Well we do and now you're in trouble!" Additionally, the real problems with pirated stuff is in the distribution of it, not the possession.