[matt_kantor]

Standard protocols and interoperability do not preclude this. Plenty of people have separate work email addresses from their personal ones.

[nl]

And interestingly most people use separate clients for their work and personal email accounts.

[shmerl]

Indeed. Separation of accounts and profiles isn't really related to artificial separation of existing services which prevents interoperability. Accounts should be separable according to user's preferences, and not according to how services decided not to federate. It's pretty self explanatory.