2 or 3 times, I set as a goal to progress through all the posters from where I stood to the far wall, and each time I had to be brusque with 2 or 3 (or more) people to continue to move on in a timely way. Lunch is a good time to have a chance to survey the posters.

It is also a challenge to watch just one talk in an oral session, especially since I like to sit in the front. Manners and a clear view of the proceedings don't mix so well.