I'm a fan of goodie bags when they are not full of junky things that we'll never use. For example, my daughter got one that had a tiny plastic slinky, a tiny thing of silly putty and some sugarless gum (which she can't have). She played with the slinky for 10 seconds, the silly putty ended up never being opened and we threw the gum away. Take the $4 that the mom probably spent on the bag times the 15 kids that were at the party and that's $60 wasted!
My daughter has gotten some wonderful goodie bags though. One had a bunch of hair rubber band in it, which we can ALWAYS use, and some hand sanitizer, which we also use a lot of.
I think it depends on what you put into the bag, and how much you have to spend.
Personally we don't do goodie bags, we usually do some sort of craft at the party and that's what the girls take home.