My computer once had a spyware infestation that none of the proprietary stuff detected. I figured these spywares are probably made by companies hawking out those obscure anti-spyware products themselves.
IIRC, I used SpyDefender, or something with a similar name...
Indeed, out of the many advertisements this spyware brings me, one of them is for an anti-spyware software.
Now why would I want to do business with them if they are going to invade my computer in this manner?