While I am not planning myself to use av on my nokia, this point is often overlooked. The scenario is this - someone forwards an infected file to you. You are running linux, and so are unaware and unaffected by the virus. You forward the file on to your mother who has let her av updates lapse. She opens the attachment because she trusts her children. Who is responsible? The person who forwarded the email to you, your mother, or you? Pick any of these and then imagine explaining it to your mother. Change the setting to one of business. You receive a doc from a business partner who has never heard of av. You forward it on to a customer who has also never heard of av. They are infected from the email you sent. Bam, they are not your customer any more. A carrier of a virus is just as culpable as someone infected by one.