Yes, the Bing example seems to give real-world validation of all this. In general it seems that hardware vs. software fit is orthogonal to concerns such as fre

Yes, the Bing example seems to give real-world validation of all this. In general it seems that hardware vs. software fit is orthogonal to concerns such as frequent reconfiguration. Some algorithms simply match hardware well (high concurrency, low-complexity control flow, able to stream through data without complex state). These are often algorithms that do not fit general-purpose CPUs well (cache hierarchy wasted on streaming; lots of control overhead; low core counts relative to FPGA-level parallelism). Some of these algorithms may be for specialized and/or frequently-changing applications such that they should not be burned into an ASIC that will live in a datacenter for 3-5 years.