The big issue with 'transferring' dashboards that use segments or bookmarks with segments etc is that the relationship gets broken when the transfers happen. The transferred dashboard/report doesn't get it's association with the transferred segment set so it doesn't know what segment to use. etc.
overall it's not really worth 'transferring' things because you probably spend more time fixing things up than you save by doing a quick transfer.
And the suggestion that you just change the password and email address for an account with someone's name attached to it so someone else can use it can cause all sorts of regulatory issues if you have any sort of a security organization.
What you need to do which is harder to govern but better in the long run is to create several login accounts as 'holders' of the shared resources like segments, dashboards, bookmarks, calculated metrics etc
What a segment is deemed to be 'approved' then you want to log into that shared account and save a copy of the segment there and share it out. Turn off the sharing of the original segment and make sure everyone uses the approved one. The same with calculated metrics etc.
This way you have a repository of the shared elements for your company login and don't need to worry about issues arising when a key employee leaves the company or moves on to another assignment and doesn't need their library of shared components anymore.
The other issue overall is there is no way to get a report of what segments/calculated metrics are used in what report/dashboard/bookmark etc so you can trace back to make sure everyone uses the correct components for reporting.
Also remember if you delete a user login then whatever ad-hoc projects they have that are not shared are no longer retrievable even if you re-create the account. So make sure you clean up ad-hoc before deleting accounts.