May I suggest that WPMU Dev create a Popup plugin.
Used wisely Popups can grab your visitor's attention instantly.
You have instant benefits like more blog subscribers, more RSS feeds subscriptions, direct people to special offers, provide effective updates, increase sales, increase leads, display an special message, etc.
Something similar to this
With effect like fading, lightBox, etc.
This is a must to increase subscription rate to our sites.
Please develop it, we need it in rush.