First things first, I have Linux, OS X, and Windows floating around my house on various machines. Secondly, as a longtime PC user (notice I did not specify which OS), I ALWAYS check anything I download from the internet, heck, I even check some software I bought from a brick and mortar store for malware. Every system in my house has an antivirus software on it, all my windows systems have anti-spyware stuff out the wazoo running, (if you know of any Mac ones, let me know) and even my Mac is set up to scan something I just downloaded before executing it. This is way overkill on my part probably since I am behind a dial up connection, so a botnet isn't exactly useful to the operator from here (not to mention my phone cords are normally unplugged, long story and lesson learned.) BUT, I have yet to have an issue with any malware around my house. I grew up at a high school as the unofficial tech guy and saw what happened to reasonable sized networks as malware got a hold in it, and as a result I vowed not to let it happen to any of my machines. Also, all the anti-malware software I'm running is only as good as the user; if someone were to disable it and do visit some nefarious stuff on my computers they would go down too. That's why I'm admin and nobody else in the household has a sudo/admin/supervisor account. So far, so good!
In summary:
Security through obscurity is NEVER something to be relied upon.
Security is only as good as the user's intelligence will let it be and in continuance,
You can't fix stupid.