Sure. WP-SpamFree works by doing the following:
2. The comment receiving side of things checks that cookie and rejects comments without it.
A better way would be the simple hidden form field. It's almost as effective and it is fully compliant with standard HTML. I use this method myself, it blocks quite a lot of spam. This method is simply adding a hidden field to your comment form and then checking for its presence in the comment. Not difficult, but spammers usually don't load your comment form, they just spam the comment directly into your blog, ignoring the form.
In the long run, however, both these methods are flawed. Bypassing either of them is trivial. And realistically, they don't address the problem: Blocking spam. Neither one attempts to block spam, they merely attempt to block automated commenting systems. Akismet and such try to detect what is spam and what is ham and let the ham through, and so are more reliable in the long run because they cannot be bypassed by the spammer.
BTW, the reason you don't get many trackbacks is that Bad Behavior tends to block them. Turn it off for a while, and you'll find a deluge of them. This is the main means spammers hit blogs, through the trackback door. Simple Trackback Validation is lightweight and blocks spam trackbacks about as good as BB does, but without the large overhead.