The thing with coffeeshop weed is that if you don't know what your looking at, or just look gullible then they will more than likely try and sell you dodgy stuff. Having said that I have found that this is only really a problem in the less reputable establishments.
I have seen shaken or skuffed weed being sold out there a lot, especially in multi gram deals and such. I carry a loupe around with me and inspect the weed before I buy it. If they have any problem with me doing this then I just go elsewhere as this speaks volumes about their produce to me.
I have seen sprayed weed out there once when I was with some friends. I think we were in Rasta Baby (used to be a good place but recently it has gone downhill with pre weighed deals that include the weight of the baggy

), anyways my mate went up and bought a bag of the not so popular weed on the menu I think it was called mixed fruits or something. He came back and opened it up and it was obvious from the offset that it has been sprayed with something dodgy, I said to take it back to the counter and exchange it for something decent which he did with no problems from the owner.
Just have a good look at your weed and hash before you buy it to inspect the quality, if they have a problem with this then go elsewhere.