With the new release of ga.js this is possible. In the old days a fired event immediately after a trackPageview would cause Google Analytics to report a 0% bouncerate for that visit. But sometimes you don't want that behavior because the event is not always triggered by the visitor.
For instance: I track page load times the same way Google Analytics does, but in an unsampled way (Google only meausures 10%). To do that I fire an event immediately after the trackPageview, but I do that in another profile with a different UA-XXXX-Y number so it won't affect my bouncerates. But now we have an extra parameter:
_trackEvent(category, action, opt_label, opt_value, opt_noninteraction)
If you set this opt_noninteraction (boolean) to true it wil not affect bouncerates!!! That makes it possible to: