As someone posted earlier, I could go to the trouble of installing software long enough to do a complete sweep, thereby proving the system is clean. But the absolutely tiny amount of malware that can even install itself on OSX simply doesn't justify the effort - hence my analogy with certain vaccinations earlier on. Why get yourself injected against typhoid if you're never going to travel anywhere you can get it?
As for viruses transferred ... what, exactly? And how? jpegs originated on my own camera and edited on my own machine? Word documents originated in NeoOffice in ODT format and saved off as MS .doc? Mpegs created in my copy of iMovie? I'm happy to be educated otherwise, but at the moment my understanding is that none of those poses a credible means of unwittingly transferring any kind of malware to anyone.
You are going to have a very, very hard time convincing me that there is any need to engage the same level of paranoia in keeping my Mac free of nasties as is clearly necessary when managing a Windows-based machine.
