The answer I guess is "It depends".

A customer that isn't running a SharePoint virus checker on his internal WSS 2.0 servers - but where every client supposedly has it's own virus checker software - was struck for the first time in about two production years by a single document containing a virus that had been uploaded to a document library.

SharePoint of course was blamed even though SharePoint was only acting as a storage location for the document and thus naturally the problem had nothing whatsoever to do with SharePoint really.

However to avoid this kind of thing in future I was asked to look at virus checkers for WSS 2.0 and that leads me to the question in the Subject line.

At tens of thousands of dollars for the number of potential users that that client has (pricing is always per seat), is it really worth it to pay just to avoid people blaming SharePoint for something that has nothing to do with it?

In this case it was annoying that in order to check this out (i.e. see for myself) I had to try to open that document only to see my own (client) virus checker grab it and thus I later needed to delete my IE temporary files to get rid of it. But is saving my annoyance worth more than a few dollars ...

My gut feeling is that it isn't and that Virus Checkers on uploads should be used mainly for sites that are open to the Internet and the potentially nasty people who are out there. But then I always was tight-fisted.