Mozy is a piece of shit. Avoid it like the plague.

My favorite bit of their crap software is freaking out at odd times on my mac and sucking all IO rendering the computer unusable. And no, not at scheduled backup times. Perhaps these morons are reading the entire backup set and rehashing it instead of watching for changes? Dunno. This behavior persisted even after I told it to stop backing anything up at all.

What I do know is the client sucks ass and the web has many stories of people unable to recover their data when they needed it.