My company has noticed that it is not possible (or at least very difficult) to have multiple people editing the same Visio document. When we tried to co-author, we would overwrite each other's changes when one person pressed save and we frequently lost meaningful edits. We now have an inefficient process of only allowing one person to work in Visio at a time. This delays our ability to complete our work on time and has the potential to cost our clients and our company hundreds of thousands of dollars.
My whole company would greatly appreciate if Microsoft would focus on developing Visio to make it easier for coauthoring/collaboration.