I unclip the M + M and take it with me, in the neoprene case. Apart from the initial installation by the dealer, the stalk hasn't been moved. Removing it as well and putting the blanking plate in place seems to be unnecessary to me. And the stalk would be awkward to carry around.
I generally leave my M&M in place, but take a view depending on where I am. If it's on my drive or parked at my kids' school, I leave it where it is. If I've parked at the local leisure centre, I tend to remove the M&M - my wife also removes the stalk but she is generally mroe cautious than me.
I live in a nice area so probably don't really need to. But I spent many years living in London and you never ever left anything like that on show unless you wanted to come back to a smashed side window. There were lots of little piles of broken car window glass at the sides of the roads where people hadn't been so cautious. My old MX5 got broken into twice in two days when I lived in Islington - all that got taken was a pair of prescription sunglasses which I'd foolishly left on view!
I've had two of the cars I've owned in the past broken into, so don't leave anything on view inside these days. I don't live in a particularly 'bad' area but it's best to remove any temptation from the equation as it were.
This is one of the reasons why I don't use M&M much - plugging it in, taking it out...it's such a palaver for the distances I travel. The sat. nav. feature is nice but I'm only likely to use it, say, twice a year. I'll miss out the M&M on my next Up purchase (two years down the line perhaps).