Steven St. Jean has written a nice post about how to assign to a particular person the work item that's created for a failed build. When he talks about the name for the Assigned To field, it must match the name that's displayed in work item tracking. WIT shows the display name for a user, rather than the shorter domain login (aka alias).
I just came across a post on the MSDN TFS forums that was asking how you go about assigning the workitem created on a failed build to a specific user. I have also been asked to do this in my organization.
Team Build will create a new workitem in your Team Project when a build fails. The "task" is assigned to the account that ran the build. In my case, that account is a build service account. One of my Dev Leads asked how we could modify the build process to make the assignment to him whenever one of his builds failed. I didn't have time to look into it, so I pretty much blew him off. I recently had some time to look back into this subject.