Someone told me today that filling in an evaluation form was a waste of time because it is completely subjective. If you like the presenter you may mark high regardless. While I agree it is completely subjective after paying $1000.00 to hear the person speak you need to think of it this way:
If the talk was no good, not on topic and you walked out learning nothing, regardless of your feelings about the way s/he looks, talks or stares at you during the presentation, that speaker was bad, the presentation was bad and all you got for your money was a wasted day!
So subjective or not the evaluation sheets are required so you ensure those who follow get what you paid for.