In is long 16 year life my cat never learned that "nothing happens besides the noise" when I was using the vacuum and always ran in terror.

The thing is, the vacuum cleaner moves around. I think that is part of the fear factor for cats.

My two were petrified of our shower when it was put in because it's quite noisy, but have both since learned to ignore it. One even sits on the side of the bath watching the water. They still hate the vacuum.

If they figure out that the blender doesn't move around the sideboard, they MAY get used to it, and the owner will end up back at square one. Of course, it goes without saying that every cat is different...

'Better safe than sorry' is normally the smart option in the animal kingdom. There was a story on the news last night about the lionfish which have escaped into the Atlantic. Apparently the native fish don't recognise them as a danger, so they don't swim away and are eaten.

No, because cats won't stay around long enough to see what happens.