I usually try to sit near the back: - I can see the audience, and who I want to network with - I can leave if the talk isn't appropriate for me - you're last to be "called on" and can choose your answer wisely - if you do want to participate, you can usually move closer-- but once you're close, it's hard to move back. - there are other, more powerful ways to indicate that you're hungry, smart, aggressive, etc.

Sitting in the back directly contributed to my first $MM: I said something pithy and then networked with the perfect two people, who I then brought into a deal that later IPO'd.

Pretty much, the only time I want to be in front, is the line to leave a burning building (or failing company).