I could be wrong but it doesn't seem like there is any code in place to update the page title with each ajax page load. I'm working on a solution and it seems to work for some pages but I haven't gotten it to work consistently. Figured I'd mention it here in case anyone else is battling against the same issue.
I'll update if I get it working. Thanks.
http://wordpress.org/extend/plugins/advanced-ajax-page-loader/