The presentation (embedded below) consists of 148 slides. Below I selected few interesting ones.

Slide 42
• Wikitravel: only 5% of those who press “edit” actually save
• Wikipedia: 1/5 to 2/5
• WikiHow: 30% with guided editing
• Wikia: WYSIWYG editor >> 50%
Sources: Jack Herrick, WikiHow; Erik Zachte, Wikimedia Foundation

Slide 91:
An experiment by The Guardian on crowdsourcing journalism.
The Guardian obtained two million pages of explosive documents that outed your country’s biggest political scandal of the decade. They’ve had a team of professional journalists on the job for a month, slamming out a string of blockbuster stories as they find them in their huge stack of secrets.
How do you catch up? If you’re the Guardian of London, you wait for the associated public-records dump, shovel it all on your Web site next to a simple feedback interface and enlist more than 20,000 volunteers to help you find the needles in the haystack.
Your cost for the operation? One full week from a software developer, a few days’ help from others in his department, and £50 to rent temporary servers.