One big issue for me is that I only have one name. I think it's asking too much of people trying to connect with me to have to choose between four Twitter accounts or 2-3 Facebook profiles.
I can't keep FaceBook (or most other social sites) in two tabs, each in a different account. As soon as you log in with the second account, refreshing the first tab will send you to the second account as well.
I really don't see the issue, and I think that's why nobody has done anything about it.