[gknoy]

I prefer to be pessimistic about other drivers' ability to judge whether they have enough room to cut in front of me. I'd rather not try to go fast enough to "discourage", as there will inevitably be some person who either doesn't notice me, or misjudges my speed (via a side view mirror) and mistakenly thinks he can cut in front of me safely.

A lower speed increases the chances of this, but reduces the risk of a catastrophic result. ;)