I'm pretty deep into the AJAX myself now, but am still fairly new to it. I think I grasp the concept fairly well though, as I've been writing all my own functions from scratch and implementing them into my company site.
I hadn't heard that about the using POST to enter data into the database (I assume you meant database and not server, as everything in AJAX is going to and from the server) and GET to get it out. The only times I have been using POST until now is when there is the potential for the information to be too long for a GET request (there is a limit to the number of characters that can be used in a GET request).
What I'm getting at is that I don't have the answer to your question! But I'm wondering about the theory behind J.K's comment. Is it a security thing? If so then I could potentially see the reasoning behind using post to enter data into the database, although if such is the case then it seems to me it would make better sense to get it out of the database with post as well. Does he elaborate anymore on the topic?