making the default install more secure

WordPress 2.6 will be more secure out-of-the box including better support for running the admin over SSL and changes to disable the remote publishing protocols by default.

We have choosen to disable Atom Publishing Protocol and the variety of XML-RPC protocols by default as they expose a potential to be a security risk.  So from WordPress 2.6 onwards you will need to go into the Settings->Write page and enable them individually if you want to use them.