I would be remiss if I didn't mention one of the biggest money wasters (and simultaneously one of the best marketing scams) that I ever came across. I went to Georgetown and our home bar just a block from campus is Tombs. Each March, the Tombs puts on a contest called the "99 Days Club". It challenges seniors to make a purchase at Tombs every single day for the last 99 days of their final semester. Those who do are rewarded by getting their name on the 99 Days Plaque for the Year which sits on the wall in the bar.
I can't even imagine how much money my friends wasted on the 99 Days Club. I was certainly a frequenter of Tombs, but even if you are going in to just buy the cheapest beer they have each day, you're still throwing away close to $400. And I know many of my friends instead would have lunch there each day for 99 days which probably amounted to close to $1500.