Well, lets take a look at Obama's cabinet (in his first term)...
Sec. of State: Clinton... as a senator served on a commission dealing with European relations, as well as the armed services committee (not to mention her series of connections from things like the Clinton Foundation, and her time as first lady)
Treasury: Geither... former president of the NY federal reserve bank
Defense: Gates... previously a member of a think tank that dealt with various middle east conflicts
Att. General: Holder... worked for the justice department and as a judge
Interior: Salazar... served in the Colorado department of natural resources
Agriculture: Vilsack... as gov. in Iowa, was involved in dealing with ethanol production
Commerce: Locke... May not have been a businessman, but he did serve as a gov.
Labor: Solis... member of several chambers of commerce and civil rights/workers rights organizations
Health and Human services: Sebelius... was on an insurance commission (so at least some familiarity with health care issues). Also served gov. of kansas (with whatever responsibility that comes with HHS on a state level)
Transport: LaHood... Was on the House Transportation and Infrastructure Committee
(Those are just the first ones I came across)
So it does look like it is more common than not to have someone with pre-existing expertise in the cabinet posting they are taking over.