I've blocked them in the past too for this, but it seems they are better behaved now. I don't have any longer term data, but over the past week they averaged 1.

I've blocked them in the past too for this, but it seems they are better behaved now. I don't have any longer term data, but over the past week they averaged 1.5 request per minute and that is divided among ~630 unique websites. Infact, the UAs I blocked are no longer in use it seems so they are no longer limited. EDIT: btw, not endorsing their search or anything, just mentioning thye may have learned and improved ;)