You can never be sure of what is too good to be true. Unlimited space/bandwidth are dead giveaways. Bandwidth is at a premium so people setting 100gb for $1/month is a good clue also. The disk space is less of a give away as we find most of our servers with the age of 80-120gb drives have less than 25% of any drive used. We are about to update our space plans again since our busiest servers still have more than 70% drive space free.