No, it wasn't me.
I'm sure it's discussed regularly but we have to base the speeds on something. Those same 777s are often the ones who "can't do" 160 kts 10 mile out!
And yes, we are painfully aware of the problems with modern aircraft and approach speeds. The number of controllers suspended recently, pending investigation of the loss of separation caused by speed control being ignored is a testament to this.
We are required to work to an approach spacing of 5 miles / vortex wake, whichever is the greater. Here's the good bit - UNLESS YOU SAY OTHERWISE, having read back "160 to 4" then that's what we are basing the speeds / vectors of the following traffic on. If you then slow to 135 knots at 5.5 dme WITHOUT A WORD (regular occurrence), then we will not be aware of the fact until the following traffic is observed to be catching up at half a mile per minute. More often than not, it is then too late to avoid the separation loss.
Take a look at this thread from more than 4 years ago Guy:
The 160 Knot thread
Typhoonpilot