Here’s an interesting thought: since AJAX applications have to use GET requests to send data back and forth between the server, one could argue that applications based on AJAX might be considered harmful, since they don’t use POST requests. The danger being that a random user could concievably follow a link to a GET request which is only supposed to happen within an AJAX application, or even worse, a search engline like Google might somehow get a hold of the AJAX GET request URL and spider it. In both of these cases, sending a GET request outside the context of the actual AJAX application would have bad consequences, and will probably modify some online database in an undesirable way.

It might sound redundant, but a GET request should always return the same results (like a search query). GET requests are useful for GETting information, whereas POST requests are useful for POSTing information. Web applications which modify online databases should use POST, but unfortuently, current implemenations of AJAX only support GET requests. It’ll be interesting to see how developers work around this issue.

edit: I stand corrected, AJAX can apparently support POSTs.