rango - 9:40 pm on Sep 14, 2012 (gmt 0)
Trying to draw a distinction between soft bounces (spends at least a few seconds on page) and hard bounces (gone within 1s) is useful for deciding what to focus your efforts on.
If they are mostly hard bounces, you can bet it's an instant decision on the part of the user; adding more content won't fix this, but improving your design, ad positioning or use of popups, etc might.
If there are a lot of soft bounces, then you can look at maybe improving the content or other links on page to try and keep them on site.
If they are spending a lot of time on the page and then bouncing, the content is probably good and the only thing to focus on would be additional calls-to-action to get them to become repeat visitors.