Then said link is in violation of web standards that have existed for literally decades. I believe I've heard stories about google bots deleting entire forums, because the forums performed destructive actions via GET calls to specific URLs.
If what you said makes sense to you, ask yourself how google can crawl any URL at all, considering communicating anything to any server could trigger a destructive action.
Beware, one of the unwritten laws of HN is that any post containing anything vaguely reminiscent of reddit gets downvoted. Upvoted in order to pre-empt the inevitable downvote.
They do and they are (at least where I have worked) but it seems that Google et. alia are smart enough to not follow links marked containing text with the value "Unsubscribe".
POSTs are not by definition idempotent. You can make a server response to a POST be idempotent but when you want multiple identical requests to have different effects, POST is the method to use (vs. GET, PUT, DELETE, etc.)
Implementors should be aware that the software represents the user in their interactions over the Internet, and should be careful to allow the user to be aware of any actions they might take which may have an unexpected significance to themselves or others.
In particular, the convention has been established that the GET and HEAD methods SHOULD NOT have the significance of taking an action other than retrieval. These methods ought to be considered "safe". This allows user agents to represent other methods, such as POST, PUT and DELETE, in a special way, so that the user is made aware of the fact that a possibly unsafe action is being requested.
Naturally, it is not possible to ensure that the server does not generate side-effects as a result of performing a GET request; in fact, some dynamic resources consider that a feature. The important distinction here is that the user did not request the side-effects, so therefore cannot be held accountable for them.
