If a site specifically bans such advertising you'll just get banned. Google is pretty aware of Backpage, Craigs, etc. Many have tried... many have failed. Spam is spam. And Classified ads are for selling items...not promoting blogs. But go ahead and give it a whirl... one less Adsense account is one less person I have to compete with.
personly speaking , it is safe ! as long as you promote your site , you can get more profits and what's more you can improve your conprehensive abilities . however , you neednot make some spams and illgial informations! please have a try!