I'll have to admit it's disgusting how often I use it, but I have definitely fallen into the ranch dressing pit of despair. I'm one of the sad American creatures that does pretty much use it with anything, especially fries and pizza. I know it looks gross and is extremely unhealthy, but I just can't help myself. So tasty...

You have to admit it's at least useful when whatever you're dipping in it wasn't very good in the first place - it covers up mediocre flavor quite well.

Edit: Also, Twinkies = same thing - one of the scariest things to come out of a factory, and yet I'm inexplicably drawn to them.