StumbleUpon: Real or Fake?

We received an email this morning from Brooke Tessman, Director of Advertising Sales for At first, I thought it was a “normal” sales call. Then, I started to think about what she was saying:

StumbleUpon offers a unique opportunity to reach the targeted audience you’re searching for. Discover great websites, videos, pictures and more-all according to your interests. Send your website or video directly to people who want to see your content. StumbleUpon shows your website or video directly to interested web surfers who have already expressed a strong interest in similar content.

Target the exact audience you want. Target visitors by category, location, age, and gender. Get valuable feedback from real people. See how many people rated your content “thumbs-up” or “thumbs-down”. Interested in learning more about StumbleUpon advertising opportunities?

What I’m interested in learning more about is… do StumbleUpon users realize they may be stumbling upon paid placements?