[brazzy]

Dude, you need to update your mental threat model. These days, there's no such thing as "safe habits" - you're up against drive-by downloads that exploit browser or plugin vulnerabilities and are delivered by all kinds of perfectly normal websites that just happen to be vulnerable to SQL injection.

[muyuu]

My cousin, for instance, uses her Mac as a word processor, email reader, Wikipedia reader or DVD player 90% of the time. Works in TextEdit, doesn't download basically anything at all. Does everything basically inside Apple's walled garden. The only "dangerous" thing she did in the past is using MSN for Windows. This could mean automatically receiving payloads and run them by just having an infected contact, because of Microsoft's "wise" defaults. This doesn't happen on Adium. I think she doesn't login to that network much anymore, now it's all about Jabber (gtalk) and Skype I reckon.

Unless Apple started injecting payloads there's basically no plausible way to get her infected. She doesn't even "browse the net" for the most part, doesn't click on links, doesn't give a f.

There are safe habits. AV companies would like to have you thinking you're always about to have your nix based system rooted, but this is damn unlikely for most people not using dodgy sites. I fancy my chances to get struck by lightning above her chances of having her system compromised, and I don't get out of my house scared.