I ran across a sentence a few days ago that sounded jarring. I had the form:
"A number of ... has ..."
I understand what the author was thinking. The word 'number' is singular, so it should have the singular verb 'has'. For some reason this just sounds completely wrong to me, though. There are plenty of words that function this way, singular terms that refer to a collection of things. Yet a number of other terms aren't like this (there we go: I used it the way that sounds right to me, and you probably didn't even notice). As I thought about it more, my thinking turned into outright armchair linguistics, i.e. ordinary language philosophy. Here is how my hearing of the terms like this (that I can think of) lines them up:
clearly singular: a group of, a collection of, a set of, a troop of
clearly plural: a few of, a number of
unclearly plural: a couple of [depending on whether the emphasis is on the couple as a unit or on the members of the couple]
no idea: a plethora of [this gets used so little that I have too small a sample on with to judge, especially given that everyone else who uses it has too small a sample on which to judge]
singular in formal English but often used as plural: each of
The last usage (the often used usage, not the formal one) sounds wrong to me, even though it's very common. "Each of them are wrong" just doesn't sound like English to me, yet I hear it frequently, especially when there are lots of words in between subject and verb. Yet "a number of ... has" sounds jarringly wrong, not just wrong. It sounds as bad to me as saying that a few of the items in my list is in the wrong place. A number of items in the list is in the wrong place.
You're not talking about the number. You're talking about the items. So 'of items' isn't functioning as a prepositional phrase modifying 'number' or 'few', as the surface grammar presents it. I'm not sure exactly what's going on, but it sounds more to me as if 'a few of' and 'a number of' have become adverbial phrases modifying 'items', which is in fact the subject of the sentence. That would explain why the verb would be plural.
Or maybe it's just that the author is Canadian.