Quote from ajaxpatterns:
" Witness the the debacle caused by the Google Accelerator interacting with non-RESTful services in mid-2005. The accelerator jumps ahead of the user and prefetches each link in case they should click on it (a non-Ajaxian example of Predictive Fetch). The problem came when users logged into non-RESTful applications like Backpack. Because Backpack deletes items using GET calls, the accelerator - in its eagerness to activate each GET query - ended up deleting personal data. This could happen with regular search engine crawlers too ... "
REST compared to RPC