To most successfully seed the online community with your branded widget, you should make it available through multiple venues. Be sure to incorporate a place for users to easily grab the widget via your destination site, as well as from the rich media portion of your ad campaign, which will inherently reach a much larger audience than your mini-site alone. Embedding the widget directly into the ad will result in a higher number of widget downloads than offering this functionality only on your website. Additionally, to fully encourage and maximize viral behavior, plan for the widget to contain an instantly recognizable call-to-action, where other users can obviously grab the widget directly for their own use. 

The payoff
Once the user encounters their first widget-equipped online ad and sees how easy it is to post this compelling digital content to virtually any social network profile or blog (e.g., Facebook, MySpace or Blogger), they may fill their sites with widgets of their favorite products or causes.

The benefits are two-fold: the advertiser's message is automatically experienced more frequently by more loyal audiences, and simultaneously by more relevant audiences, as the widgets are voluntarily posted to sites or profiles that users have a personal relationship with, such as a coworker's blog or a friend's profile.

Another payoff for users is that these widgets allow them to "wear" brands or causes as a "badge" -- a way of defining and reflecting who they are to their peers. In these "green" days, a user might embrace a widget of an environmentally-friendly cause or company, which allows them to reinforce their online identity as one who truly cares.