I built a system for a lady at South West Rocks early last year. She rang me and explained that she had been exceeding her download limit with her Telstra ADSL plan for the past few months. (a 200Mb plan mind you) The Telstra tech person told her she might have spyware leeching her data.
She wanted to know if I'd installed spyware on her computer.
Now when I built the system I installed all my usual spyware removal/prevention tools. I explained the concept of spyware then showed her how to update and use them. This was an extra hour of my time.
I also transferred all her data from the old system. I explained all this and informed her that her data while interesting to her, was of absolutely no interest to me.
She says "Well its certainly of interest to someone!" then hangs up in my ear.