I think HFCS has slightly addictive qualities. I'm not backing this up with any evidence!

Found this study on Reuters the other day.

http://www.reuters.com/article/idAFN0210830520100802
Cancer cells slurp up fructose, US study finds | Reuters

As a general rule of thumb I steer clear of processed food, mostly because it tastes like crap compared to something I cooked, or buy from a bakery.