Bit of a spin off of this question...
Do you tell the client if you are sub-contracting their work? Morally is it an obligation, or do you pass it off as your own?
When choosing collaborators, do you work with people who have a similar design style as you, or someone who produces a completely different feel? How does this effect how you present that work to clients?
Do you position your business as an individual designer or a studio/agency ('I' vs 'We')? If 'We', do you use collaborated work in your portfolio? Where do you draw the line between an agency/studio reel and falsely taking credit for someone else's work?