Sharing lessons learned between developers is essential to making software development faster, more efficient, and more accurate. Giving developers good tools to edit and create wiki pages is one way Microsoft is trying to encourage the spread of information between devs. Now it is easier than ever in Visual Studio Online to use wikis and improve them for your fellow dev.
Implementing wiki edit and creation tools is a big win for companies who need to maintain their software for a long time. When developers are writing code they are problem solving, and good developers document the process of overcoming problems. Inexperienced programmers may not leave a good trail of bread crumbs to lead themselves or others to fix issues in the same way.
Different methods for problem solving can lead to jumbled code and errors in the final product. Then when the development team is working through code they need to know how the code works and what different elements do. Without resources like wiki's the code documentation process can be painful and developers could be dissuaded from doing a good job.