During my studies I got to interpret countless speeches simply to practice or to prepare for exams. And I always kept score. Most students (including myself!) would overuse filler words such as "like", "um", "okay". This is mainly due to the fact that interpreters need to deal with complex sentence structures during the translation process, containing rhetorical devices, subordinate clauses and possibly unknown words. And the next thing you hear is a distracting filler word, because an interpreting student is at a loss for what comes next. Being a professional interpreter, I have adapted other and more elegant techniques to fill a silence (the so-called décalage).
Next time you listen to somebody speak, try to pay attention: It's surprising just how much we use filler words, sometimes even too much ;-)