"StumbleUpon discovers Web sites based on your interests, learns what you like, and brings you more." It's a network that can result in a lot of wasted time and a lot of interesting sites. I'm a regular user myself. When I read this post a short while ago about the Stumble Effect, basically that someone discovered a lot of site traffic coming from StumbleUpon, my interest was peaked as I've seen the same thing happening with GottaQuirk. Herewith, a few stats and numbers on StumbleUpon. There is less available than I would have like to find but I thought it interesting nonetheless.

From Compete (April 2009)

Unique Visitors: 4916 224

From LinkedIn - Stumble Upon Company Profile (April 2009)

• More than 7.4 million users
• 425 million recommendations per month
• 32 employees
• 87% male
• there are more than 20 000 advertisers using the service

From StumbleUpon (April 2009)

• 7,495,965 users

From TechCrunch - StumbleUpon, A Case Study In The Efficient Allocation Of Resources (April 2009)

• Comscore shows StumbleUpon with the same number of unique monthly visitors today, 1.5 million, that they had two years ago.

From Quantcast (April 2009)

Users are:

• 51% Male
• 49% Female

From Read Write Web - StumbleUpon Hits 7 Million Users, Quietly 50% Bigger Than Twitter (February 2009)

• The social discovery network, like Pandora for webpages and videos, just passed 7 million users according to the site. That's about 50% bigger than Twitter, though Stumble is rarely talked about and never promoted.