You can use the htaccess to protect yourself against referral spam or bad bots. You can also google bad bot traps to protect against bad spiders but then you might have to expressly allow certain agents like google, msn, yahoo etc. in your robots.txt.
Another very handy function of the htaccess is hotlink protection. For good tutorials and an intro to the htaccess google ilovejackdaniels . Gotta love that site 