A lot of valid discussion here regarding bird strike risk, originating from a convention (converted to a rule, but never a law) that aircraft be restricted to 250 KIAS below 10000 feet. Unfortunately, a great many birds exceed the statutory limit of 10000 feet, thus, if bird strike risk was a significant factor, we should lift the limiting altitude even higher. Like most of the posts here, I'm digressing from the intent of the original post, so let's put birds aside for the moment.
The origin of the rule, and indeed it's fairly recent application in Australia, stems from the desire to more effectively regulate traffic flow, and this it does. Fortunately, Australia is possessed of Air Traffic Controllers who recognise it as a convention, and apply a certain degree of flexibility in this, and a number of other conventions WHEN TRAFFIC FLOW PERMITS. The Aussie controllers, for example, frequently allow cruise at non-standard levels when traffic permits, and speed in excess of 250 KIAS below 10000 feet when traffic permits - Indeed it may improve traffic flow to have someone fly faster to increase the spacing with slower traffic behind.
For a great number of heavy aircraft, my own included, the aircraft flies like a brick at 250 KIAS with much reduced manoeuvre margins. I note that for my own aircraft, minimum manoeuvre speed at Max Weight is 248 KIAS, providing protection of a mere 1.2 G before stall, turbulence penetration speed of 280 KIAS provides 1.6 G protection, just enough to tolerate MODERATE turbulence. When I'm facing stormy turbulent conditions in Australian terminal areas, I advise of a REQUIREMENT to increase speed, not a request, it's a safety issue. Thank goodness for the flexible and practical Aussie controllers, and the Yanks at 'inflexible' LAX, and the allegedly 'VERY inflexible' Taiwanese controllers, etc. etc. I suppose that, in the terms of reference used by one of the contributors here, I'm a macho pilot - No Sir! I'll leave the macho stuff to the guys who want to go do stalling practice in thunderstorms with 350 to 400 passengers on board.
There's minimal commercial advantage in maintaining high speed below 10000 on descent, but to insinuate that 320 KIAS at ATC request down to 4 or 5000 feet is macho stuff is plain ridiculous and an insult to capabilities of the thousands of VERY conservative airmen who do it every day.