It seems that the most effective Web 2.0 tools are those that allow you to accomplish something quickly and easily. Twitter is a good example. At a most basic level, you blog in 140-character increments. Type and submit. No manual required.
Screenr definitely fits the ‘ease of use’ description. It is a quick and easy way to create screencasts. When I visited the site, I looked for an “about” section. Prominently featured on the site is a “one-minute tour“. I watched the tour and, though I haven’t tried to create a screencast yet, I feel like I could create one after watching that one-minute video.
I think screencasts could be very effective in the K-12 environment. Technology integration staff could create a library of “how-to” screencasts and direct teachers to them when faced with repetitive questions. Teachers could create screencasts for any number of reasons and show them to students as part of their lessons. Students could create screencasts as part of a “show and tell” to demonstrate knowledge on a particular subject.
I’m not saying all of this would happen immediately but, if it doesn’t, it shouldn’t be because there wasn’t an easy way to do it. Give it a shot!