Quoted from pinball_keefer:

The biggest problem with simply ignoring a troll is that occasionally you have to put them in their place, especially when you perceive they are affecting your ability to put food on the table for you and your family.
If people had an ignore count next to them (ie how many times they had been ignored by others) then maybe ignoring would have some value. But depending on your situation it probably doesn't make sense to simply put your head in the sand.
But I've also spent most of my life online and gotten into many flamewars over the years, so I am probably just predisposed to arguing on the internet.