Usage and limitations of sponge functions for PRNG This HRNG uses SHA3 as a sponge function (in its device driver) to inflate ots raw source output to many MByte/s. They compare this output rate to the output of other HRNG which don't use a sponge function. I'm wondering if this comparison is fair and brings me to the question to which extend a sponge function should be used to inflate RNG. The goal should be to get entropy suitable for cryptographic operations (e.g. key generation).

Edit: In other words, if a sponge function could be used to inflate 300 kByte/s to 500 MByte/s without reducing the entropy, why--talking Linux--to use /dev/random in favour of /dev/urandom at all?
I'd say the comparison table is not a fair one, as it compares the Infinite Noise generator's throughput when feeding bits into a CSPRNG (Keccak) running on the host workstation and then running that CSPRNG as fast as the workstation allows. Other devices in the table achieve ~10 Mbit/sec speeds, but all of those devices in the table which had enough design documentation published on the web seem to advertise their throughput based on whitened output, but not on output expanded via a seeded CSPRNG on the host. 

All of this is “much ado about nothing” however. A single 256-bit seed and a fast-key-erasure CSPRNG is all one should ever want in the real world. Don't create a persistent channel for attacker-controlled input. Or just use /dev/urandom.