I recently commented on Entrecard's plan to cut down on users' bounce rates. For those unfamiliar with the term, bounce rate is the rate at which users "bounce" to another site instead of staying and visiting more posts within your blog. Having too high of a bounce rate can apparently have a negative affect on your page rankings.
So what I think about banner exchange programs and bounce rate? I still think traffic is traffic. Here's what I mean: you are probably not going to get a huge number of hits from banner exchange programs. If banner exchange is giving you a really high bounce rate, then you probably don't have that much traffic in the first place and need all the help you can get.
Let me give you an example. I've been using Adgitize for my fitness blog for a few months now. I get an average of about 50 hits a day on that blog from Adgitize campaigns. Does it affect my bounce rate? I doubt it, since my fitness blog has been averaging 700-1,000 hits a day. In other words, those 50 extra hits just don't make that much difference.
This blog, on the other hand, is a different story. I get around the same number of daily hits from Adgitize (maybe a little less), but this blog gets under a hundred hits a day overall. The bounce rate may hurt this blog's rankings, but its either high-bounce traffic or no traffic for now. I'll take the high bounce traffic over no traffic.
I'm not an expert on this kind of thing, but this is what I'm thinking for now.