If it's only a protocol violation, I guess Facebook can use JavaScript to generate a POST request instead. And in fact, they should be doing so.
The permissions and responsibilities of a user should not be associated with the type of request. Although it's true that users should not be responsible for a GET request, but the retrieval is based on the web page itself. The Facebook SDK will generate other requests automatically because the permissions have already granted. The GET request is only the trigger. (Imagine you have already agreed to post everything on ReadWriteWeb to Facebook through their reader app by a POST request, all these are hidden until you read an article. The side effects were already generated.) So I think this is not a protocol violation.
You're totally missing the point. The author points the fact that issuing "GET /interesting-article.html" should NOT have any side-effect. This is the GET that should not have any side-effect. The other GET or POST or whatever it is is the side-effect.
The author goes as far as criticizing other side-effects already in place; an example of which is ads. Because you see when you browse an article about Herpes, then you encounter ads about Herpes drugs on every website.
I got hit by this while looking for paid webmails. After a few searches on Google, I started to see ads for atmail on every single page.
There are people who believe it's a violation and I'm one of them.
EDIT: please don't point at Do Not Track or other work-arounds because that's all they are.
The permissions and responsibilities of a user should not be associated with the type of request. Although it's true that users should not be responsible for a GET request, but the retrieval is based on the web page itself. The Facebook SDK will generate other requests automatically because the permissions have already granted. The GET request is only the trigger. (Imagine you have already agreed to post everything on ReadWriteWeb to Facebook through their reader app by a POST request, all these are hidden until you read an article. The side effects were already generated.) So I think this is not a protocol violation.