The "saved topics" option has taken over the basic favorites-saving function that the personal topics list once served, but there are two situations where you may still want to use the personal topics list instead:

1) You may want functionality similar to saved topics but with subcategories for organization ("saved topics" has no subcategories, it's just a list). You can let people add existing topics from your directory into their personal topics list and its subcategories using this template code:

<IF {TID} does not contain albums>
<form action="http://scripts.webmastersite.net/wsnforum/manual/albums.php?add={TOPICID}" method="post">
Add to <select name="subalbumid">{THISMEMBERALBUMLIST}</select>
<input type="submit" value="Add" />
</form>
</IF>

To allow people to remove a topic from their list, place this by it:

<IF {TID} contains albums><a href="http://scripts.webmastersite.net/wsnforum/manual/albums.php?todo=remove&linkid={TOPICID}&catid={TOPICCATID}">Remove</a></IF>

Thanks to the conditionals, you can put these in the topic bit and the add form will only show outside of the personal topics list while the remove link will only show inside the personal topics list.

2) You may want to let people add new topics that aren't in the directory. This is mostly useful for WSN Gallery, where members can have their own personal albums of their own images which aren't mixed with the site's images.