After adding another person to my ignore list today, I noticed that my list now weighs in at a mighty 58 users. That means I have more people in my ignore list in this one forum than in every other forum that I've ever been a member of combined.
If you don't agree with someone, or they annoy you, just skip over their posts - it's not that difficult. Plus, that way if you feel the need to contribute to a thread in which they are involved, you can at least see the ENTIRE conversation instead of only parts of it. Besides, anyone who really annoys me that much, I simply enjoy flaming them until the thread gets locked anyway :P
I don't use ignore lists. As deggis said, they don't solve any problem. On top of that, even the most stupid forumer can from time to time say something intelligent, and the most intelligent one can say something stupid.
To me, a huge ignore list is just the symptom of a failure.