Comic sans is one of the most used and also most hated fonts in the world. It was created in 1994 by Vincent Connare to be used in a comic. It was designed to be friendly and playful and to appeal to children. If that is your intention and audience, Comic sans should be your font of choice.
Every font has a character and an impact. This meaning is principally culturally based and is subconscious, not learned. It is the express purpose of the font designer to communicate in this way. The popularity of the Comic sans typeface is presumed to be due to a combination of the attractiveness of a simple (sans serif) typeface and its perceived friendly and attractive nature. For this reason it became very popular for children’s party invitations, birthday cards and, unsurprisingly, comics.
Comic sans is a joke though. It is intended as a jokey font. This fact is not affected by the ignorance of presenter. A presentation using comic sans, intentionally or otherwise suggests that content should not be taken seriously. It is like using clip art. Comic sans was developed for comics. Unless your presentation is a comic, don’t use comic sans.
addendum
I’m intrigued at the response to this post on Twitter. Let me be clear that anyone can use any font they want in a presentation. I’m certainly not The Font Police. The point I was simply trying to make is that the cultural view of this font will significantly affect the reception of your presentation whether intended to assist dyslexics, make it friendly or because you feel it is lighthearted.