Purpose of 1000mbps network interface in SATA NAS

With Comex around. People started supporting their favorite brand names. Of the NASes, Linksys NAS200 and D-Link DNS-323 are quite hot during this computer fair.

Quite a handful of people pointed out that NAS200 simply cannot make it due to its bad performance and urging people to either get the D-Link DNS-323 for its 1000mbps interface or Planex NAS-01G for its user support in hardwarezone forums.

Of cos, there would be people pointing out the bad points of DNS-323. One particular comment actually caught my attention. The user commented:

what is the purpose for giving a 1000mbs network port for a SATA harddisk with less than 500mb read or write speed?

Well, without much thinking. I replied that at that SATA speed, it is well in excess of a 100mbps NAS and the NAS would be limiting the performance of the SATA harddisk. Why would one put a high performance hardware into something that lower its performance so drastically? Why not get a 1000mbps NAS and utilize up to 500mbps read or write speed even if the 1000mbps is not fully utilized. Lastly, if 100mbps is preferred over 1000mbps, it is better to get a IDE NAS as both of them are a better match than SATA with 100mbps network port.