asp.net mvc - Why should you delete using an HTTP POST or DELETE, rather than GET?

Question

I have been working through Microsoft's ASP.NET MVC tutorials, ending up at this page

http://www.asp.net/learn/mvc/tutorial-32-cs.aspx

The following statement is made towards the bottom of this page:

In general, you don’t want to perform an HTTP GET operation when invoking an action that modifies the state of your web application. When performing a delete, you want to perform an HTTP POST, or better yet, an HTTP DELETE operation.

Is this true? Can anyone offer a more detailed explanation for the rationale behind this statement?

Edit

Wikipedia states the following:

Some methods (for example, HEAD, GET, OPTIONS and TRACE) are defined as safe, which means they are intended only for information retrieval and should not change the state of the server.

By contrast, methods such as POST, PUT and DELETE are intended for actions which may cause side effects either on the server

question from:https://stackoverflow.com/questions/786070/why-should-you-delete-using-an-http-post-or-delete-rather-than-get

Answer 1

Jon Skeet's answer is the canonical answer. But: Suppose you have a link:

href = "myAppDeleteImportantData.aspx?UserID=27"

and the google-bot comes along and indexes your page? What happens then?