Its very common in college.
I actually think, it is not only a conversational placeholder, but also used for rythm od the story, to give the story timing, in an attempt to make it more entertaining.
Uh, um, and you know, are also commonly used.
I worked in technical support with a guy, ex gang banger, that was always saying, "you know what Im sayin'?" I pointed it out to him, and he was surprised, adn stopped.
I have tried ot get rid of it. It is very strange to tell a story using he said "blah blah blah" then she said "blah blha blah", to which he retorted "blah blah blah". I found myself stammering quite a bit.