stumble upon is one of the Best social bookmarking site that finds and recommends web content to its users. This is in list of top bookmarking sites.

1. STUMBLE UPON
A SOCIAL BOOKMARKING SITE

2. WHAT IS STUMBLE UPON ?
• StumbleUpon is a discovery engine (a form of web search engine) that finds and
recommends web content to its users. Its features allow users to discover and
rate Web pages, photos and videos that are personalized to their tastes and
interests using peer-sourcing and social-networking principles.

3. HISTORY
• StumbleUpon was founded in November 2001 by Garrett Camp, Geoff Smith, Justin LaFrance
and Eric Boyd during Garrett's time in graduate school at the University of Calgary.
• The idea of creating a company was established before the content: of the five or six ideas for
products, StumbleUpon was chosen.
• Garrett describes in a BBC interview the moment for him in which he felt the company had
really taken off: "When we passed the half a million mark (in registered users), it seemed more
real.“
• The popularity of the software attracted Silicon Valley investor Brad O'Neill to take notice of
the company and assist with a move to San Francisco, as well as bringing in subsequent fund-
raising totaling $1.2 million from other angel investors including Tim Ferriss, Ram Shriram
(Google), Mitch Kapor (Mozilla Foundation), First Round Capital and Ron Conway. Ferriss,
Garrett Camp and Geoff Smith all live in San Francisco, where StumbleUpon is headquartered.

4. OWNERSHIP :
• In May 2007, StumbleUpon was purchased by eBay. Early reports indicated that
the company was also in talks with Google and AOL before the eBay
announcement.
• In September 2008, eBay hired Deutsche Bank to try to sell StumbleUpon again.
• On April 13, 2009, founders Garrett Camp and Geoff Smith, and other investors
including Ram Shriram, bought the company.

5. GROWTH OF NETWORK
• StumbleUpon claims to have more than 10 million members as of 18 May 2010.
StumbleUpon said that before the end of May 2008, it would have collected its
five-billionth "stumble", more than one billion of which would have taken place
in 2008 alone. In August 2011, StumbleUpon reached the 25 billion stumble
mark, at which point they were adding over 1 billion stumbles per month. In
April 2012, StumbleUpon announced that it had over 25 million registered users
of the service.

6. TRAFFIC ON SITE
• According to a 2013 fourth quarter Shareaholic's Social Media Traffic Report,
Stumble upon accounted for more publisher traffic than YouTube, Reddit,
LinkedIn and Google combined.
• Over 100,000 publishers, brands and marketers use Stumble upon's advertising
and content distribution platform in order to promote their products and
services. Stumble upon now serves over 125 million brand and publisher
sponsored placements per month

7. HOW TO ADVERTISE
• Paid Discovery is StumbleUpon’s ad system. StumbleUpon’s platform lets users surf the web by Stumbling to sites
that match their interests, simply by hitting a button on their browser or mobile device. With Paid Discovery, an
advertiser’s URL (website, video, etc.) becomes part of that stream.
• Up to 5% of all stumbles are reserved for Paid Discovery where the advertisers directly insert their web page into
the user experience. This means the audience lands directly on their web pages, videos and photos. Users can also
provide feedback (thumbs up / thumbs down) on this content.
• Since Paid Discovery sends visitors directly to the advertiser’s page, there’s no need to create an ad; the
advertiser’s entire web page is the ad. When an ad is delivered to a user, a green icon or “Sponsored” will appear
in the toolbar or mobile app, denoting a paid stumble. StumbleUpon doesn’t serve typical display ad formats,
such as pop-ups/interstitials, banners, etc.

8. HOW IT WORKS
• StumbleUpon uses collaborative filtering (an automated process combining human
opinions with machine learning of personal preference) to create virtual
communities of like-minded Web surfers.
• Rating Web sites update a personal profile (a blog-style record of rated sites) and
generate peer networks of Web surfers linked by common interest. These social
networks coordinate the distribution of Web content, so that users "stumble upon"
pages explicitly recommended by friends and peers.
• Giving a site a thumbs up results in the site being placed under the user's "favorites".
• Furthermore, users have the ability to stumble their personal interests like "History"
or "Games"

9. INFORMATION MODEL FOR USERS

10. SERVICES
• Two services that are added later :
i. Stumble Video
ii. Stumble Thru
iii. Su.pr

11. STUMBLE VIDEO
• On December 13, 2006, StumbleUpon launched their Stumble Video site .The new site allows
users without a toolbar to "stumble" through all the videos that toolbar users have submitted
and rate them using an Ajax interface. The site currently aggregates videos from College
Humor, DailyMotion, FunnyOrDie, Google, MetaCafe, MySpace, Vimeo and YouTube.
• StumbleUpon launched a version of Stumble Video for the Internet Channel Web browser that
runs on the Wii console on February 12, 2007. This version of Stumble Video is optimized for
the Wii's smaller screen resolution and offers similar functionality to that of the original version.
• In September 2013, StumbleUpon acquired 5by, a video discovery app created by Greg
Isenberg.[18]

12. STUMBLE THRU
• n April 2007, StumbleUpon launched the StumbleThru service, allowing users of the toolbar to
stumble within sites such as YouTube, The Onion, Public Broadcasting Service and Wikipedia.
According to the announcement of the feature, StumbleUpon plans on adding additional Web
sites in the future.
• As of June 13, 2010, sites using StumbleThru include BBC.com, Blogger, Break.com, CNN.com,
Collegehumor, Flickr.com, FunnyorDie.com, Howstuffworks.com, HuffingtonPost.com,
Metacafe.com, Pbs.org, PhysOrg, Rolling Stone, Scientific American, The Onion, Wikipedia,
Wired.com, WordPress and YouTube.
• The StumbleThru service allows registered users to stumble on specific sites like the ones listed
above, rather than the entire Web.

13. SU.PR
• In March 2009, StumbleUpon launched Su.pr, a URL shortening service. It is
primarily used to link to Twitter and Facebook statuses and updates.This service
is similar to that of bit.ly and TinyURL. From March through May 2009, the su.pr
service was only available to people who had received an invite code, but later,
it was made available to all StumbleUpon users. In 2013, StumbleUpon
discontinued the su.pr service to focus more on their lists feature.