Do not ever ever advertise with StumbleUpon. There is a user there named "suhallofshame" who finds people who use this service, and has a whole army of people thumbs-down advertiser's sites. The result: you spend money to have this guy make the entire StumbleUpon community give you bad reviews.
His motivation: advertisers = spam, and spam should be killed. If you advertise with StumbleUpon, your website is committing suicide
