[raldi]

"However, this is not completely true. It means: it won't change the resource representation. It is still possible, that safe methods do change things on a server or resource, but this should not reflect in a different representation."

http://restcookbook.com/HTTP%20Methods/idempotency/

[lifthrasiir]

It is possible to do so but may not be desirable anyway. It is completely possible to wire a fork bomb to the safe methods; you probably don't want to enable the bomb via crawler however.

[cname]

I don't think that's referring to a case like this. I'd also argue that voting _does_, slightly, change the representation.

[raldi]

Only in the same way that watching a YouTube video changes the view count. Do you believe that's an invalid use of GET?