Update their PageRank algorithm to take into account website speed, and then publish this as a fact.
The idea would be that they would have GoogleBot measure the latency, and overall page load time and rank sites higher that respond faster, and slow sites lower.
One of the problems with PageRank is that most of how they measure site quality is a mystery, but making it plain that speed is used in ranking would bring website performance to the front of everyone's minds. They could use similar metrics as YSlow and PageSpeed use, and tell everyone to optimize their sites using those tools as a starting point.