Yes I do, but not very often.
When do I unfollow?

When I get tired of massposting in my reader. It could be good posts, that I like, but when one or two bloggs appears with “one million” posts in a row, then the selection of posts in my reader gets smaller.

I can’t read posts from that many blogs that I want to, when I catch posts in the reader, which I do most.

I often have bad connection, so visiting blogs takes hours to upload just for one blog. The reader is a shortcut to every blog I follow. But to get there I have to have at least one post showing in the reader.

When one or two blogs occupies nearly the whole reader flow, nearly all of the others seems to disappear.
It’s like when someone claim a whole train and only sits on one seat.

Massposting may be an effective way to catch readers, but I think it also can create irritation. If you want to post a lot, then why don´t you schedule the posts with some timespace instead. Then your posts will appear often in the reader, but still let other posts get through too.

I’m just saying what I think, you don’t have to agree with me.

I discovered that I don’t like when my reader only shows a few bloggers post, so I probably will unfollow such blogs in the future too.

So, if you think I visit your blogs too seldom, this could be a reason. I don’t see your posts in my reader.