You are right, it does take scale to do this well. I'm CEO at Skimlinks, so although a little biased, I can assure you Skimlinks is at the same if not greater scale. Our uptime and speed is the best in the industry, as you can see from our public pingdom page http://api-status.skimlinks.com/554403/2012/10
And all this is while processing 230million clicks a month. Even Hurricane Sandy didn't affect our uptime. Our CTO wrote a great piece about it here:
http://blog.skimlinks.com/2012/10/25/the-importance-of-globa...