Every couple of months someone reminds me that I have a LinkedIn account by sending me a connection inviatation. This time, I followed the link the endorse the inviter. As part of that, I have to select a relationship. Unfortunately, LinkedIn is tied to the Old World notion that people make connections by working in the same company. I couldn't choose something like "I've worked with him on an open source project".
I realize that the endorsements verify the employment data, but I don't have to work for the same company to verify that. It's the general failing of all these sorts of networks for me. I just don't fit into their models.