My company recently posted a notice that said we are to fly the speed we are told to fly. So if we are told 160 to 4d then that is what we are to do (ie not 170 or 150). I imagine there were problems with ATC which resulted in this notice.
The thing that I find confusing is when we are told to maintain a speed like 180 knots (this happened today in fact). Then we are cleared to join the localiser, etc. No further mention of speed, how long we are to maintain 180 etc. This kind of thing happens all the time and quite frankly, if we are given a speed to maintain and then cleared for the ILS and there is no instruction to maintain until a certain point (ie outer marker or 4d), then we usually reduce speed according to SOPs. Saying "maintain 180 knots" 15 miles out is fine but when we are at 6 miles and still flying 180 generally we start getting antsy and will start slowing down unless ATC tell us first.
This does create confusion usually, and a little conversation occurs between the captain and FO about just what ATC want us to do. Usually, at times when ATC require speed control like this it is too difficult to get a word in so this is why pilots take matters into their own hands. If ATC want us to maintain until further notice, then it would really help if they told us for how long. And then try not forget about us. In the UK this is usually not so much of a problem but in Europe (read Spain) it happens all the time and if you follow ATC instructions to the letter then you will be crossing the threshold at 180 knots. We have to reduce at some safe point, and this is probably why people appear to violate the instruction, when in fact they may think they have been forgotten about (again).
lazlo