I think we can all agree that auto-playing content is an annoyance, particularly when that content is a noisy ad. Google is improving its Chrome browser to get rid of this annoyance, while improving browser performance and battery life on mobile devices.
As Myce reports, Google will use an algorithm to determine which content on the page isn't central to it (e.g., Flash advertisements). That content will be paused until you click on it to play it.
While this is bad news for advertisers--they'll have to come up with another way to make sure we see their ads--it's a boon to consumers. In addition to decreasing annoyances and possibly extending battery life, preventing banners from automatically playing could help prevent Flash-based exploits from running.
This change is rolling out September 1st.