First, it's not about "saving face"; it's about correcting misinformation.
Your assumption that the OP is talking about the file quarantine feature is just as much an interpretation as others' assumption that the OP is referring to AV software. Surely, you've been around long enough to know how many come to this forum with incorrect information. The OP said "antivirus", so it's perfectly logical to believe they meant what they said, unless they clarify otherwise.
I'm curious to know why you think my "wording is incorrect".
And while "that may very well change", we're operating in today's world, not a speculative future.
I am sure the OP believe's what they said. They simply think it is "anti-virus software." However, the clue they give is that it works with "Mail, Safari, iChat." What "antivirus" software would be so limited in scope? Within moments of reading the question I understand what the OP was referring to despite them calling it "anti-virus."
What bothers me is that many of the respondents here were so eager to tell someone they were wrong and recommend the use of "MRoogle," that they missed the opportunity to see what the OP was referring to, correct them and offer the answer.
Since everyone had done the work of telling the OP that there is no anti-virus software built-in and there are no viruses, I didn't feel the need to belabor that point anymore in my response.
I have had this argument with someone else here, but I don't really like the statement "There are no viruses for OS X." Namely because it isn't necessarily true. A more accurate statement would be "There are no known viruses currently being distributed on Mac OS X."
I don't understand the point of your last comment. Of course we live in todays world, and in todays world there exists in Snow Leopard the ability to detect malware which could prove useful in the future. The speculative future could be today, with that next piece of software you download.
Why would you want antivirus on your mac?
A few reasons.
1. If you work in an environment that consists of PCs and Macs, Macs are capable of passing a Windows virus, so Antivirus software on the Mac adds an extra level of protection for Windows users who think they are getting a trusted file.
2. If you are a cautious individual.