Well if you missed it, back in the day, places like Download.com or Source Forge would have a little pre-clicked link to "add <name>search toolbar to my browser!" which, after you downloaded your think would leave you with a browser that always redirected your search requests to what ever company paid to send you there.
Lots of people did it, even Blekko (although we stopped after we figured out it was just a scam), and the way it worked is toolbar company X would approach your internet site and say "we can send you a lot of traffic, just use this toolbar, we'll even pay you every time one gets installed."
Anyway, the toolbar would hook itself into the address bar and search selection hook in the browser and redirect every search to where ever it was told to. The nefarious part is that these tool bars were often shipped to the company as binaries not source, so you didn't really know everything they were doing. Once we figured out they were scumbags we also found out that they did some really scumbaggish things.
We stopped using them but lots of people did and finally the browser makers re-wrote the browsers to make what they did either impossible or easy for the user to revert and those guys rolled up their shops and went on to become some other type of scam.
Lots of people did it, even Blekko (although we stopped after we figured out it was just a scam), and the way it worked is toolbar company X would approach your internet site and say "we can send you a lot of traffic, just use this toolbar, we'll even pay you every time one gets installed."
Anyway, the toolbar would hook itself into the address bar and search selection hook in the browser and redirect every search to where ever it was told to. The nefarious part is that these tool bars were often shipped to the company as binaries not source, so you didn't really know everything they were doing. Once we figured out they were scumbags we also found out that they did some really scumbaggish things.
We stopped using them but lots of people did and finally the browser makers re-wrote the browsers to make what they did either impossible or easy for the user to revert and those guys rolled up their shops and went on to become some other type of scam.