Just today I saw a SPAM thread in the Buy & Sell forum; it a quite a few hours old and had twenty views, but it was still there. Remember, when you see a thread or post that you think is SPAM, report it by clicking the report button located on the top bar of every post (all the way too the right, on the same bar the time of the post is). I use the Classic vBulletin theme, so depending on the theme you use, the button may be in a different spot and look differently.