Currently the list of link types (eznode, ezobject, Ftp, File, Http, Https, Mail, Anchor, Other) is hardcoded in extension/ezoe/design/standard/templates/ezoe/tag_link.tpl. The only way to change something in it (name, order, remove one type, ...) is to override the template. (for example a lot of end users don't understand the difference between eznode and ezobject and they usually only need eznode links, file and ftp types are rarely used/useful, ...)

In addition it's currently very difficult to add a type of link. It would be useful to be able to write an extension that adds a new link type.
Examples of use :

1. in my blog, I select "Other" and then I type tags/keywords/weblog/ez_publish to link the list of blog post related to eZ Publish, with the right extension installed I could select a "tag" link type and then just type the keyword or select one in a list)
2. another extension could add a "wikipedia" link type, when you select it, you just have to type a word to generate a link to a wikipedia article
3. ...