Ideally, yes. And that's certainly how companies are marketing their free AVs. The reality is that before we started signing all of our software, the free AVs detected it as a virus.

It's bad for business when you have to defend your product as not a virus (on top of trying to sell it!)

I wrote about it 2 years ago: http://wyday.com/blog/2007/useful-instantupdate-feedback/