Answer:
1. Stage fear
2. Unadvisable manarisms like putting your hand inside your pocket, holding your shirt button etc...
3. Easily confunded by jokers among the listeners
4. Brooding over the same topic for a long time
5. Tone less speech
6. No sense of humour
7. Not looking into the eyes of the audience
There are many of such kind. I like seven as I am a fan of Harry Potter and so I gave only seven observable Disadvantages....