Yes, they are also CPA.

We've also got something similar to them, in that we can rewrite links on the fly, converting them into revenue-earning links, if they match one of our merchants.

Yep, Skimlinks also do the link conversion as well.

And so does VigLink, and arguably at greater scale...it takes scale to do this well. VigLink claims to have over 30,000 merchants.

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...