I just turned off the "Likes" for my blog post about "vegemite" asking readers to go in my Poll (which is in another of my blog posts, together with the history of vegemite), because I don't like people simply "liking" my posts just to get exposure or coverage (i.e. to have their gravatars/profiles there) and I suspect that has often been the case for my posts. However, to my surprise, today I got email notifications that there had been 3 "Likes" of my post.
I went to the Reader in WordPress and sure enough the Like option is there along with the excerpt of my post.
I am not actually showing the "Likes" on the actual Post in question, but still I would like the function of fully disabling "Likes" so the option doesn't show up in the Reader, but rather, having the Like option only available at the bottom of a post (and not via the Reader).
This would stop "likes" from the Reader where the liker has not read the whole post but is just passing by and clicking Like here and there based upon the extracts, simply to get exposure.
I know that having the "Like" option in the Reader makes it quick and easy to like a post from the Reader, but speaking for myself, I am more interested in Comments than Likes, and if someone really does read and like a blog post, by clicking on the title or "read more" from the Reader, he/she could just as easily "Like" the post from below the Post.
A word of warning
If you have happily posted several blog posts with "On for all posts" and then you switch to "Turned on per post", this change will remove all the Likes that your existing posts have obtained.
So, if you want the Likes for all or some of those to be shown, but not for your new post, then you have to zandyring's method - edit the post and uncheck "Show Likes". :)