Hey, yeah the spammers use "bots" and "spiders" to crawl the internet looking for files named "guestbook.php" and they can post to them even if they aren't members or signed in. If you have disabled it in admin and aren't going to use this feature the quickest way to solve the problem is just to delete guestbook.php from your dolphin directory.. I did it on all my sites :-)

thanks
Mike
http://www.makeasocialnetwork.com