I don't THINK it was hacked. I know it. How do I know it?
I use my Slingbox to watch sporting events when I'm at my business. That is the only use. Further, I know nobody with that particular email address.
I have removed the user, but I have screen captures of all of it. Further, the guy posted the same email address on a FB thread to get game cheats of some sort, so I know who it is.
What is Slingbox doing to secure accounts? Given the number of threads about hacks on these forums, the answer appears to be "not much."