That's the first thing I noticed. What was used instead of Warp?
I also see that Snap got pulled in a couple days ago, so it will probably get tested in the next round. Should be interesting to see how it fares against Yesod.
The way the benchmark is constructed, it's really more about JSON and DB performance. Snap makes no decisions for you about those things, so the numbers really won't reflect the performance of Snap all that much. I don't have great expectations for the "Snap" code that is in there now because it is not using very fast JSON and DB libraries.
Actually, the performances of Yesod are not so bad, as Play's are.
Top performing frameworks (netty, vertx, go) are not web frameworks but async programming frameworks. They don't carry a lot of things around -- just push the serialized data on the raw socket output stream. Yesod/Play/Django/Rails/... on the other hand must manage routes, content types, browser headers, etc etc....
I also see that Snap got pulled in a couple days ago, so it will probably get tested in the next round. Should be interesting to see how it fares against Yesod.