It took a while to find out that bbPress 0.9.0.5 doesn't use pagination on the frontpage.
Having more topics than what is set in admin under 'Items per page:' will make the older ones disappear.
It took a while to find the plugin 'Topics Per Page' ( http://bbpress.org/plugins/topic/front-page-topics/ ) which gives you a pagination bar with page numbers.
Installation went easy, putting it in the my-plugins/ folder after setting the number of topics or posts I wanted on each page. Edit topics-per-page.php to do this.
Now in front-page.php you still have to place the call for the function front_page_pages(); AFTER <?php endforeach; endif; // $topics ?> </table>
Sure putting this code in the file and not activating the plugin first will make your frontpage stop running after this call. It's better to check first 'if function_exists'
In my front-page.php it looks like this now:
<?php endforeach; endif; // $topics ?>
</table>
<?php if (function_exists('front_page_pages')) { ?>
<div class="nav"><?php front_page_pages(); ?></div>
<?php } // end front_page_pages ?>
Where the first two lines should be already in your file!
Finally in readme.txt it says 'if you use rewrite slugs you MUST add a rule to your .htaccess'
The suggested rule RewriteRule ^page/([0-9]+)/?$ /forums/?page=$1 [L,QSA] works well if your forum is installed in a folder called /forums/
I installed it in the root folder of a subdomain, so for this installation I used
RewriteRule ^page/([0-9]+)/?$ /?page=$1 [L,QSA]
Now I enjoy pagination on the frontpage of bbPress, thanks to the Contributors _ck_ and mdawaffe