If WordPress spam concerns you, there are some plugins and extras that you might find useful, namely: Akismet, Anti-Spam, reCaptcha, and Comment-Control. These are available on blog.inf, but will need to be activated from your blog dashboard.
…is a hosted web service that automatically detects comment and trackback spam. It’s free for personal use, but you do have to register for an activation/API key.
Akismet should automatically divert spam to the Spam bucket. It’s hosted on external servers, but accessed through plugins or directly via the API. Each time a new comment, trackback, or pingback is added to your blog, it’s submitted to the Akismet web service which tests it and returns a thumbs up or thumbs down – so you don’t have to check each one yourself.
For more details, see http://akismet.com/.
…blocks spam in comments automatically. It works by adding two extra, hidden, fields to the comments form – which are intended to foil automatic generation of spam comments.
Note that Anti-Spam doesn’t particularly care about anonymous posts – it’s just supposed to trap automatic posts…
For more details, see http://wordpress.org/plugins/anti-spam/.
…utilises the reCAPTCHA anti-spam library to help your blog stay clear of spam (especially when integrated with Akismet). Unlike the current WP-reCAPTCHA plugin, this one has a different approach and allows you to customize how the captcha looks using CSS.
It’s free for personal use, but you do have to register for an activation/API key.
For more details, see http://betterwp.net/wordpress-plugins/bwp-recaptcha/.
…allows you to set the default comment status independently for different post types (Posts, Pages, etc), as well as tweak a few other things like the comment status on attachments. You can also bulk-edit the comment status on all your posts at once.
Comment Control allows a more configurable approach to leaving comments, but may not worry too much about spam as such. If you restrict comments, then you restrict the potential for spam.
For more details, see http://wordpress.org/plugins/comment-control/.
On a more general note, you may also want to check how you include images in your posts, making sure that you use “Media File” as your Link To setting, rather than “Attachment Page” (the latter allows comments to be added to the attachment page, which is probably not what you want).