SOCAL will do this pretty routinely sequencing arrivals into LAX. The most common practice is to assign 250 knots at some point, then slow you to 210, then assign 170 or 180 "to the marker" (about 5-6 mile final), at which point you'll be slowing to your target approach speed. So mostly commonly, they are only assigning speed reductions. However, there are times when they want you to close up space on the aircraft ahead, so they might speed you back up again until the extra distance is closed up -- at which point they slow you back again.
These instructions are always given with the implicit understanding that, if you can't do it, you'll say so... "XYZ123 is unable 250, I can give you 225" or something similar. If you've already extended flaps so that the higher speed would be near or over an aircraft limitation, that could be a reasonable reply. (Of course, if you extended flaps 20 miles out from the runway, maybe retracting them again & not annoying SOCAL might be a wiser course of action.)
Depending on the aircraft type (how fast you can fly clean, and how quickly you can slow to your approach speed so that you are stable for the approach at 1000' - or whatever your OpSpecs/SOP's require), you might be given something else. Light aircraft are often told to keep a fairly high speed (for them) to the marker, since otherwise they're like bicycles on the freeway & slowing down everybody behind them. On the other hand, they can often decelerate more rapidly than some jets, so staying fast until close in may work out just fine. Again, if the controller is assigning a speed that's too fast until too close, it's the pilot's job to say, "unable."
The controllers at SOCAL are excellent at knowing what the aircraft they're working with are capable of, and they are very good at timing the speed reductions so that you end up with about 3 miles separation on short final, so that the runway usage is kept high... as one aircraft is turning off the runway, the next jet is a mile or so out. Much closer than that & you risk go-arounds if somebody gets nervous or the turning-off aircraft isn't expeditious; much farther than that & you aren't landing planes as quickly as what you could be.
Some controllers match the proficiency of the ones at SOCAL; others don't compare. Of course, you don't really expect the controller at Podunk to have the same practice in setting up a string of aircraft coming in one after another as those in SOCAL, NORCAL, ATL, ORD, and so forth. The good ones will use all the tools at their disposal, and sometimes this will include having one aircraft increase their speed for a while.