Commodity server gear is really cheap, and is more or less "fast enough". The wins from serving say, >1Tbps from a 1U box with an ASIC or FPGA is negated by the downsides of having such a large failure domain, and the cost of development for what would be a pretty low volume part.

We talk about this stuff every once in a while, but it doesn't really make sense to do right now. (Disclaimer: I work at Netflix)